An "incendiary device" ignited inside a package at a U.S. Postal Service processing center in Washington on Friday, just hours after Maryland officials warned that the threat against government agencies — from someone described as a likely "lone wolf" — continues.
The parcel was similar in design and shape to the two received Thursday in Maryland, which were addressed to the governor in Annapolis and the state's transportation secretary in Hanover and accompanied by identical handwritten notes.
But Friday's package widened the sender's target list to include federal officials. It was sent to Homeland Security Secretary Janet Napolitano, according to a department official who spoke to the Associated Press on the condition of anonymity because of a continuing investigation.
"We just don't know where this person is going," Maryland State Police Superintendent Col. Terrence B. Sheridan said earlier in the day during a news conference at the agency's headquarters in Pikesville, cautioning that other mailings were likely.
Sheridan's officers had cleared more than 400 state mailrooms to resume operation after employees swept them for suspicious packages Friday, when a third incident was reported inside a postal facility in the 3300 block of V St. in Northeast Washington.
Cathy Lanier, chief of the Metropolitan Police Department in Washington, said the package was discovered, unopened, about 2 p.m. by a postal employee, after it ignited in a "brief flash of fire and extinguished itself."
The employee flagged down a police officer, and emergency teams from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives responded, among others. No one was injured.
Lanier said Washington officials put precautions in place Thursday after the Maryland events, knowing that "incidents that occur in one jurisdiction are not necessarily" limited to those areas. She declined to confirm the intended recipient of the package.
The District of Columbia package brought new agencies into the joint federal and local investigation and further heightened concerns for law enforcement officials. But it didn't appear to alter the working theory: that the sender is angry with some faction of government.
"This was an act done by a sole individual, who, for whatever reason, wanted to send a message," said Rep. C.A. Dutch Ruppersberger, a member of the House Intelligence Committee.
He made the statement during a telephone interview Friday afternoon, before the discovery of the Washington package, and confirmed the analysis through a spokeswoman afterward, adding that the three packages appear to be linked.
Sheridan of the Maryland State Police confirmed Friday that investigators are looking for one or more potentially "disgruntled" people who "may have a vendetta" against the state government.
"We're not sure what we have here," Sheridan said. The existence of the Washington package is likely to broaden the scope of the investigation, officials said.
If caught, the perpetrator could be charged with felony possession and use of an explosive device, which carries a maximum prison term of 20 years.
Maryland investigators were combing through phone calls, e-mails and letters that might shed light on potential suspects, though none had been identified as of Friday. Members of known terrorist organizations, such as al-Qaida, were ruled unlikely, however.
"If they're going to do this, it would have been a bomb. This was not a bomb, it was a smoke cloud," Ruppersberger said.
The Maryland packages were addressed to Gov. Martin O'Malley at a building in Annapolis and to Maryland Department of Transportation Secretary Beverley K. Swaim-Staley at the agency's headquarters in Hanover.
They were affixed with 44-cent stamps and delivered in white boxes that were about the size of a VHS cassette tape, 7 1/2 inches long, 4 inches wide and 1 inch deep, Sheridan said. The district package was "similar in nature," according to Lanier.
She declined to say whether the district package contained a note like those in the Maryland parcels, which read "Report suspicious activity! Total [expletive]! You have created a self-fulfilling prophecy." They were signed "X," and one appeared to be a photocopy of the other.
The comments and MDOT target led investigators to believe that the sender was referring to highway safety signs. At least one of the Maryland packages had a return address that was traced to a Washington parking garage, Ruppersberger said.
As of Friday, it was still unclear what kind of device or flammable material was enclosed in the packages. Each will be examined for forensic evidence at an FBI facility in Quantico, Va.
Both state employees who opened the Maryland packages singed their fingers, though neither was seriously injured. Earlier reports had said just one employee was burned.
In an e-mail sent to state employees Friday morning, O'Malley asked for "continued vigilance" and reassured workers that his office is "taking this matter seriously."
O'Malley had made a joke to reporters Thursday about how he shouldn't be targeted before he makes the state budget cuts, and he chose not to hold a public briefing on the incident.
He defended the decision Friday during a news conference on the Eastern Shore.
"We determined pretty quickly it was not a device that would cause damage or harm. And we didn't want to overplay it," O'Malley said. "Once we decided it was not the type of thing that would have caused bodily harm I went ahead with my normal schedule. I felt it was inappropriate to call a press conference over what was a sparkler."
However, he suggested that state agencies may improve their mail-screening processes.
Maryland mailrooms were quarantined Thursday, though most had reopened by Friday at lunchtime, after searching for packages similar to those that ignited. Nothing was found, Sheridan said.
At the Harry R. Hughes Department of Transportation Building in Hanover, a spokesman said Friday that the mailroom had not returned to full service, however, pending some additional training for employees. The package sent there made it to the building's fourth floor, where Swaim-Staley's offices are located. The Annapolis package was opened in the mailroom.
No fresh mail will be accepted for processing at the transportation headquarters until the mailroom returns to normal service early next week.
"This is not a prank; this is serious business, it impacts our lives and causes great concern," said Sheridan of the state police. "This is not a way to get your message across."
Baltimore Sun reporters Michael Dresser, Jamie Smith Hopkins, Nick Madigan, Annie Linskey, Yeganeh June Torbati, Childs Walker and Timothy B. Wheeler contributed to this article.