A statement from Hungary's foreign ministry said U.S. authorities had reported that they had recovered the body of a female Hungarian citizen missing since Wednesday's accident.
The girl's body was recovered at around 4:45 a.m. near the Walt Whitman Bridge by members of the Philadelphia Fire Department, said Coast Guard Petty Officer Crystal Kneen. The bridge is down the river from the site of the collision.
As divers began preparations to haul the sunken boat from the water Friday morning, television cameras captured the image of a body floating face-down near the salvage site. The body surfaced briefly before submerging again.
Police did not immediately comment on whether it could be the body of the missing 20-year-old, but Lt. Frank Vanore confirmed they were searching for the body.
The Coast Guard had said Thursday evening they did not believe either of the missing passengers had survived.
The Georgia company that owns the duck boats operation said Thursday it had followed safety recommendations following a 1999 sinking, but it suspended its operations nationwide.
The missing were among 13 Hungarian students, two Hungarian teachers, four U.S. students and three U.S. teachers on a tour hosted by Marshallton United Methodist Church in suburban Philadelphia.
Istvan Nagy, a deputy mayor in Hungary, told state news agency MTI that authorities were helping the families of those involved in the accident, including the quick processing of passport requests so parents could travel as soon as possible to see their children.
Salvage crews began preparing to raise the sunken boat shortly before 9 a.m. Friday, Philadelphia police Lt. Andrew Napoli said. The effort was put on hold, however, while divers sought out the second body.
Crews working from a barge planned to lower chains down to the sunken duck boat, run them under its hull and lift it up like a sling. The fact that the boat is resting on a gravel bottom should make the process easier than if it was silt, Napoli said.
Tina Rosebrook, 30, of Davidson, N.C., told The Associated Press that she was briefly under the bow of the barge. She'd had time to get lifejackets on her 10-year-old daughter and 12-year-old niece but not herself. When she surfaced, she found one floating on the river - and discovered the girls were safe.
Police rescue boats arrived and helped them out of the water almost as quickly as they'd been submerged.
On Thursday, National Transportation Safety Board Investigators dug into their efforts to reconstruct what went wrong. They expected to spend more than a week working in Philadelphia before heading back to Washington, D.C., and continuing their investigation.
Board member Robert Sumwalt said the agency would look into the condition of the vessels and whether proper protocols were in place and were followed. The NTSB planned to interview those aboard the boats, listen to recordings of radio transmissions and study videos from cameras posted nearby by the City of Philadelphia and at least two television stations.
Sumwalt said the experience and condition of the two-member crew of the duck boat and the five-member crew of the tug would be checked out. He said tests showed none had been drinking. Drug test results were expected in about a week.
The duck boat company, Ride the Ducks, has been in Philadelphia since 2003. Passengers are driven on a tour of the Old City neighborhood near Independence Hall before riding into the Delaware River from a ramp south of the Ben Franklin Bridge.
As of 2000, there were more than 250 refurbished amphibious vehicles in service nationwide among various operators.
In Pennsylvania, agencies ranging from the Coast Guard to Philadelphia's streets department have a hand in regulating the duck boats, which look like boats with wheels.
The Coast Guard performs annual inspections of the vessels' seaworthiness, and because they travel city streets they are also registered with the state Department of Transportation.
Inspection records for the sunken duck boat have been turned over to the NTSB.
Thirteen passengers were killed when a duck boat in Hot Springs, Ark., sank in 1999, the most deadly accident since the boats were converted for tourism. Afterward, the NTSB recommended tour operators modify the boats to increase buoyancy so that they won't sink even if flooded.
The Coast Guard, which regulates most of the boats, responded in December 2001 with new safety guidance to operators but declined to mandate more buoyancy. Many operators complained the modifications were impractical, a notion the NTSB disputed.
Sharla Feldscher, a spokeswoman for Ride the Ducks, which was acquired by the Herschend Family Entertainment company, of Norcross, Ga., in 2004, said the company added buoyancy to its boats.
"If there were requests for modifications from the NTSB, they were done," she said.
The tour company suspended operations nationwide Thursday, a day after suspending its Philadelphia tours. It also operates tours in San Francisco, Atlanta, Newport, Ky., and Branson, Mo. A Ride the Ducks operation in Seattle is independently owned and remained open for business.
Contributing to this report were Associated Press writers Patrick Walters, JoAnn Loviglio, Randy Pennell and Michael Rubinkam in Philadelphia; Peter Jackson in Harrisburg, Pa.; Joan Lowy in Washington; and Pablo Gorondi in Budapest, Hungary.