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.

Members of the Coast Guard look Thursday for two missing tour boat passengers on the Delaware River in Philadelphia. The passengers’ amphibious craft in which they were riding was struck and sunk by a barge Wednesday.

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 consul 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.