PHILADELPHIA - Sandy Cohen looked up from the deck of a small, amphibious tourist boat stalled in the river to see a barge towering three stories above and approaching fast, clearly not about to stop. Then came the screams.

Over the next few seconds of terror, she and other passengers fumbled to put on life jackets and sought cover as best they could. Next came a crash, the boat flipped over, and 37 people aboard were plunged into the Delaware River.

Cohen came to the surface, clinging to the life jacket she had managed to snag seconds before. A Hungarian teenager on the tour was hanging onto the jacket, too.

A photo obtained by Philadelphia television stations shows the barge as it rides up on the stern of the sightseeing "duck" boat and starts pushing the vessel underwater. It would sink to the bottom of the Delaware River.

Two other Hungarian passengers, part of the same language program as the teenager who shared Cohen's life jacket, remained missing late Thursday, a day after the accident. The Coast Guard suspended its search for the two, 16-year-old Dora Schwendtner and 20-year-old Szablcs Prem, just before 7 p.m. Thursday. Petty Officer Crystal Kneen says the Coast Guard searches only "as long as the possibility of survival is there."

The boat had no history of mechanical problems before it caught fire, said Chris Herschend, president of Ride the Ducks, the Norcross, Ga.-based company that owns it. He said the captain appears to have followed all proper procedures during the emergency. The company hoped to raise the boat soon.

The crews of the tourist boat and a tugboat pushing the barge tested negative for alcohol. Drug test results were not expected for about a week.

The first sign of trouble came when smoke started to roll out of the boat's engine as it entered the water, the 67-year-old Cohen told The Associated Press in a phone interview Thursday from her home in Durham, N.C.

The tour guide told passengers that a tug boat would be on its way to carry them back to shore, Cohen said. She was on the phone with her husband to let him know she'd be late before the call ended abruptly - as other passengers began screaming.

"Someone said, 'Oh my God, there's a barge coming, and it doesn't look like it's stopping,"' she said.

She grabbed for a life jacket from a hook above her seat as the boat was struck and started to sink. She was quickly underwater, grabbing the jacket with one hand as her feet tangled up with those of others.

When she surfaced, she said, she realized a girl was also hanging onto the jacket.

"I just told her, 'Don't let go,' and made sure we both stayed calm," she said.

They were rescued five to 10 minutes later.

"It was a very harrowing experience. It was surreal," Cohen said.

The Hungarian group on the tour was hosted by Marshallton United Methodist Church in suburban Philadelphia. It included 13 Hungarian students; two Hungarian teachers; three U.S. teachers and four U.S. students. The church planned a prayer service for Thursday night.

The two Hungarian teachers returned to the accident scene Thursday as a part of group that included Philadelphia Mayor Michael Nutter and a Hungarian consulate representative. Nutter said he apologized to the counsel and the people who were on the boat.

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.

The six-wheeled duck boat had just driven into the river Wednesday afternoon when it had a mechanical problem and a small fire, authorities said. It was struck about 10 minutes later by the barge, and capsized.

Most of the people aboard 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 connecting Philadelphia to New Jersey.

Ten people were taken to a hospital; two declined treatment, and eight were treated and released, a hospital official said.

The National Transportation Safety Board said it would try to obtain any radio recordings, any possible mayday calls, photographs from witnesses or people aboard and other evidence over the next several days.

The Coast Guard received a transmission over an emergency channel around the time of the collision, Capt. Todd Gatlin said, but no voices or other recognizable sounds could be discerned. Gatlin likened the transmission to radio interference, but said that discovering its origin would be part of the NTSB's investigation.

Another passenger on the duck boat said she heard the captain calling for help - and moments later she was under water.

"The last thing I remember hearing was (the duck boat captain) on the radio saying, 'Whoa, whoa, whoa!"' said Tina Rosebrook, 30, of Davidson, N.C., who was touring Philadelphia's historic sites with her 10-year-old daughter and 12-year-old niece.

Rosebrook said there was less than a minute from the time the barge was spotted until the crash. She got life jackets on the girls, but not herself, and she ended up underwater against the bow of the barge, which dwarfed the tour boat, sticking 30 feet out of the water.

"I can feel the barge kind of on top of me," she recalled. "I'm feeling it with my hands."

She came to the surface and found a life jacket floating nearby. By then, she said, the girls were safely floating with other passengers. Police helped them get out of the water within a few minutes.

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.

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, Gatlin said.

A duck boat sank at Hot Springs, Ark., in May 1999, killing 13 of the 21 people aboard after its bilge pump failed. The NTSB blamed inadequate maintenance and recommended that duck boats have backup flotation devices. In June 2002, four people were killed when an amphibious tour boat, the Lady Duck, sank in the Ottawa River near Canada's Parliament.

Contributing to this report were Associated Press writers Maryclaire Dale, JoAnn Loviglio, Kathy Matheson, Randy Pennell and Michael Rubinkam in Philadelphia; Peter Jackson in Harrisburg, Pa.; and Pablo Gorondi in Budapest, Hungary.