(AP)Searchers plied the murky waters of the Delaware River early Thursday for two passengers missing from an amphibious sightseeing boat that was struck by a barge, flipped over and sank.
The 37 people aboard the six-wheeled duck boat were tossed overboard when the tugboat-pushed barge hit it after it had been adrift for a few minutes with its engine stalled, police said. Most were plucked from the river by other vessels in a frantic rescue operation that happened in full view of Penn's Landing, just south of the Ben Franklin Bridge.
The duck boat, which can travel seamlessly on land and water, had driven into the river Wednesday afternoon and suffered a mechanical problem and a small fire, officials said. It was struck about 10 minutes later by a barge used to transport sludge and sank to the bottom of the river.
The Coast Guard said it would search through the night for a 16-year-old girl and a 20-year-old man believed to have been aboard the duck boat. Senior Chief Bud Holden said Thursday that passenger interviews indicate the missing were members of a Hungarian tour group.
"Hope is fading, but we're not giving up hope completely," Coast Guard Capt. Todd Gatlin said Wednesday night.
Ten people were taken to a hospital; two declined treatment, and the other eight were treated and released, Hahnemann University Hospital spokeswoman Coleen Cannon said.
The National Transportation Safety Board said it planned to try to obtain any radio recordings, any possible mayday calls, photographs from witnesses or people aboard and other evidence as its investigators remain in Philadelphia over the next several days.
NTSB member Robert Sumwalt said investigators would try to figure out why the vessels collided and "how conspicuous would that duck have been" to the tugboat pushing the 250-foot-long barge. NTSB officials also hoped to conduct witness interviews, he said.
Police Commissioner Charles Ramsey said divers found the duck boat in water about 50 feet deep. Crews would not attempt to recover it until Thursday at the earliest, police spokesman Lt. Frank Vanore said.
There were 35 passengers and two crew members aboard the boat, Holden said. Coast Guard boats assisted by police and fire crews worked to rescue people from the water, he said. A spokeswoman for the duck boat company, Ride the Ducks, said 39 people were aboard, and the reason for the discrepancy was unclear.
One passenger, Kevin Grace, 50, of St. Louis, said he had less than a minute to get a lifejacket on his 9-year-old daughter before the barge hit.
"We had 45 seconds to try to get the life jackets on our kids," he told The Philadelphia Inquirer newspaper. "Everyone panicked, rushing to the front of the boat."
Bystanders along the waterfront screamed as the barge hit the boat, said a security guard who was patrolling the area.
"I whirled around as the barge began to run over the duck boat," said Larry Waxmunski, a guard for the Delaware River Waterfront Corp. "After the barge hit it — it almost looked like slow motion — the duck boat began to turn over."
Television footage showed at least five people being pulled from the water wearing life vests in an area of the river near the Old City neighborhood, popular with tourists. Helicopter footage showed people in life vests being helped from boats onto a dock and at least one person on a gurney.
Terri Ronna, 45, of Oakland, N.J., said she was on a ferry going from Camden, N.J., across the river to Philadelphia when the captain announced that there was someone overboard from another ship and that they were going to rescue him.
"We were not even halfway over when they said there was somebody overboard and we were going to get them," Ronna said. "There were people all over; we could see all these orange life vests."
The passengers who were treated for minor injuries and released from the hospital were three teenagers, three younger children and two adults, Cannon said.
One crew member from the duck boat was rescued by the ferry that the Delaware River Port Authority was operating on its scheduled route between Philadelphia and Camden, authority spokesman Ed Kasuba said.
Officials said the barge was owned by the city and being directed by a tugboat owned by K-Sea Transportation Partners, of East Brunswick, N.J.
The city Water Department uses the barge to transport sludge from a sewage plant in northeast Philadelphia to a recycling plant downriver, mayoral spokeswoman Maura Kennedy said. The city has a contract with K-Sea, which operates the tugboat that pulled the unmanned and unpowered barge.
Ride the Ducks also operates tours in San Francisco, Seattle, Atlanta, Newport, R.I., and Branson, Mo. The company said in a statement on its website that it was suspending its Philadelphia operations.
"Our thoughts and prayers are with our Philadelphia guests, crew members and their families," the statement said.
Holden, of the Coast Guard, said the duck boats are inspected annually, but he did not know when the boat involved in Wednesday's crash was last inspected.
Another Coast Guard spokesman, Thomas Peck, said neither craft was in a wrong lane.
Some of the duck boats are amphibious military personnel carriers dating to World War II that have been restored and reconditioned. Known by their original military acronym as DUKWs, they were first introduced in the tourism market in 1946 in the Wisconsin Dells, where about 120 of the vessels now operate.
As of 2000, there were more than 250 refurbished amphibious vehicles in service nationwide, the NTSB said.
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Five boaters spent hours stranded in the waters of the Chesapeake Bay after their 14-foot power boat capsized Saturday, floating in the water before they were rescued by the crew of a sailboat returning from a regatta.
"We motored over and saw three people clinging to a small overturned boat," Vazzano said. The crew on the Wharf Rat called mayday, alerting the Coast Guard of the capsized boat near the 
