The search for Annie Le turned into a hunt for her killer Monday after police found a body and ID'd 24-year-old graduate student behind a wall Sunday evening.

The grim announcement was made on the day that Le was to be wed.

The body was found at 10 Amistad St., a research building of the Yale School of Medicine complex, where Le was last seen. New Haven Assistant Police Chief Peter Reichard said that state police found the body about 5 p.m.

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The body was found inside a chase, a square area in a wall used to run pipes and wires from floor to floor. Police would not say in what area of the building the body was found. Le's family has been contacted, Reichard said.

Investigators hunkered down on the crime scene Monday morning, sealing off a building that had been open to Yale employees and contractors while the search for Le continued through the weekend.

The building is closed to all students and employees as the investigation continues, according to Dorie Baker, a Yale spokesperson.

Contractors hired to remodel a portion of the building were told to halt work and have been questioned by investigators.

An FBI agent was seen at a nearby Lowe's hardware store purchasing a number of large blue tarps. The agent declined to comment but said such tarps are often used to block the view of a crime scene from the public.

Police put up crime scene tape and have blocked off streets leading to the building. The road closures snarled morning traffic and forced police to reroute motorists down one-way roads in both directions.

Yale University officials are planning a candlelight prayer vigil for Le at 8 p.m. Monday on Cross Campus at the Ivy League university. An e-mail to the Yale community invites participants to "bring a candle and join us in solidarity."

Yale President Richard C. Levin met this morning with a group of Yale community members in Annie Le's academic area and briefed them on the status of the investigation and steps Yale has taken to assist it, said Yale spokesman Tom Conroy.

Levin was joined by the University Chaplain, the head of Yale's mental health services, the dean of the graduate school and the dean of the medical school, as well as campus security officials, Conroy wrote in a release.

Meanwhile, Yale Vice President Linda Lorimer reported that those with essential research responsibilities in the Amistad building are being accompanied into the building by police. Others in the building are being given an extra day of paid time off. When the building does reopen, there will be extra security at the facility for the foreseeable future.

Also, Yale has increased security and police patrols on the streets in the area and added a new bicycle patrol. Yale also added security personnel inside Sterling Hall of Medicine, where Annie Le had her lab, Lorimer said.

By the end of the day, the university expects to have a web page for updates on the investigation at http://opa.yale.edu/investigationupdate.

A Yale employee sitting outside Sterling Hall of Medicine, where Le left her purse and cell phone before going to the 10 Amistad St. building, said it is unnerving that it appears Le was killed in a Yale building that can be accessed only with a swipe card.

"We're all up in arms that it could be an employee," said Gail Novey, who works in pediatrics at the university, said this morning.

Still, she said, Yale is generally a safe place to be.

"They are very safety conscious, I'll tell you that," she said of university administrators. She said the university sends out e-mail alerts to employees and students when there is a serious crime, and that it has been notifying the Yale community of developments in Le's disappearance.

Donna DeMarinis, who sat outside with Novey, said she noticed Yale bicycle police riding by more often than usual today. DeMarinis works for Yale-New Haven Hospital.

A first-year graduate student who also sat outside Sterling Monday said she was one of the many people to receive the e-mail last night about the discovery of a body inside 10 Amistad St.

"I was shocked because it was in the building," said the woman, who asked not to be named because a killer is now at large.

She doesn't usually carry Mace, but she was sure to drop some in her backpack.

"I just put it in my bag last night," she said.

Le, from Placerville, Calif., was to have been married Sunday at the North Ritz Club in Syosset, N.Y., to Jonathan Widawsky, a graduate student at Columbia University in New York. Police have said that he is not a suspect and is helping with the investigation.

New Haven police are now the lead investigators in the case, which is considered a homicide investigation. Yale University police, the FBI, state police and the New Haven state's attorney's office are assisting with the investigation.

Reichard would not say if police have any suspects.

"Detectives and investigators right now have a large amount of physical evidence at the scene, which they're going through to determine" if it's relevant to the investigation, he said.

From about 10 a.m. Sunday to sundown, law enforcement officials were at the lab building on Amistad Street. Search dogs were brought into the building. Late in the afternoon, two flatbed trucks entered the parking lot of the lab building and took up position as if ready to haul away trash containers.

Saturday night and for much of Sunday, investigators searched the Connecticut Resources Recovery Authority's trash facility on Maxim Road in Hartford. Investigators wearing protective clothing sifted through piles of trash with machines and dogs.

Reichard said that the search was done as "a routine part of the investigation" in an attempt to follow the trail of any trash that came out of the New Haven lab building. He did not say if the search yielded any clues.

Shortly after Reichard made his statement, Yale President Richard C. Levin gave a brief press conference on the university's campus.

"Our hearts go out to the family of Annie Le, to her fiancé, to her friends," Levin said. "The family and fiancé and friends must now suffer the additional ordeal of waiting for the body to be positively identified. I met earlier this evening with Annie's family and with the fiancé and his family and I conveyed to them all the deeply felt support of the entire Yale University community."

He added that Yale has "pledged the university's full resources" for the investigation.

On Friday, Yale said that it would offer a $10,000 reward for any information that led to Le's whereabouts.

Le entered the laboratory building about 10 a.m. Tuesday and that was the last time she was seen. Officials viewed the building's security tapes repeatedly for any evidence that she had left the building but found none.

A friend said Monday the doctoral student never showed signs of worry about her own personal safety at work.

"If she was concerned about (it) she would have said something to someone and they would have known," Jennifer Simpson told CBS' "The Early Show." "And Jon (her fiance) would have known, her family would have known, friends would have known."

Simpson called Le, a pharmacology student from Placerville, Calif., friendly and affable to everyone.

"She was a people person," Simpson said. "She loved people. She loved life. We just can't imagine anybody wanting to harm Annie."

Another friend, Laurel Griffeath, echoed those thoughts on NBC's "Today" show.

"I can't even imagine someone mad at Annie, much less wanting to hurt her," Griffeath said.

The building where the body was found is part of the university medical school complex about a mile from Yale's main campus and is accessible to Yale personnel with identification cards. A network of some 75 video survelliance cameras are trained on every door.

Campus officials have said that the security network recorded Le entering the building by swiping her ID card about 10 a.m. on Sept. 8, and have been baffled before Sunday's gruesome discovery that she was never seen leaving.

Le wrote an article that was published in February in the medical school's magazine. The piece, titled "Crime and Safety in New Haven," compared higher instances of robbery in New Haven with cities that house other Ivy League schools. It also included an interview with Yale Police Chief James Perrotti, who offered advice such as "pay attention to where you are" and "avoid portraying yourself as a potential victim."

"In short, New Haven is a city and all cities have their perils," Le concludes. "But with a little street smarts, one can avoid becoming yet another statistic."

Le, who worked in a laboratory in the five-story building's basement, was reported missing Sept. 8. Her ID, money, credit cards and purse were found in her third-floor office.

More than 100 local, state and federal police had been searching the building for days, using blueprints to uncover any place where evidence or Le's body could be hidden.

Investigators on Saturday said they recovered evidence from the building. Police sources told The Courant that bloody clothing was discovered above a ceiling tile.

On Sunday morning, a state police van drove down a ramp into the building's basement area. Authorities also sifted through garbage at a Hartford incinerator Sunday, looking through trash that was taken from the building in the days since Le went missing.

Yale students on Monday called the finding sad, but some said the discovery doesn't make them feel less safe at Yale.

"Obviously it's a city and there are safety concerns," said 18-year-old Peter Spaulding, a student from Maryland. "It can happen anywhere. You have to go on with life."

Law student Lindsay Nash of West Chester, Pa., said she doesn't sense a heightened level of fear on campus.

"There's always an attention to safety here," she said. "I think there's perception that you need to be careful regardless."

Information from the Associated Press was used in this report.