PHILADELPHIA - Fox 29 has learned the two people missing in Philadelphia's duck boat crash are from Hungary.

Also, the sunken boat has been located in the Delaware River but it is in a deep channel that yields no visibility to divers.

Recovery efforts are under way Thursday morning but are being hampered by the underwater visibility described as being just 4 inches at the wreck scene.

"We're still searching with some hope. As I mentioned last night, I have to admit hopes are fading, but with some hope that they have survived," U.S. Coast Guard Deputy Sector Commander Capt. R. Todd Gatlin said during a news conference Thursday morning.

Divers could not determine if any bodies were inside the boat, authorities said.

"They could be in the boat. They could be other places. So, we're still searching," Gatlin added.

Watch Live: 12 P.M. NTSB News Conference

More Video: Amphibious Vehicle History | Pier 34 Attorney Interview | Coast Guard News Conference

Witnesses told Fox 29 an 250-foot barge being pulled by a tug boat slammed head on into the duck boat Wednesday afternoon.

The tourist boat had stalled out when a fire occurred in the engine about 10 minutes after entering the water, and the boat was drifting when it was hit.

A total of 37 people were onboard at the time, and 35 were pulled from the water. The missing are a 16-year-old girl and a 20-year-old man from Hungary.

The National Transportation Safety Board is sending agents from Washington, D.C., to investigate the crash.

The boat now sits at the bottom of the river in about 40 feet of water near the Independence Seaport Museum. The Army Corps of Engineers located the boat with SONAR, and divers marked its location with a buoy so a salvage company can come in and recover the wreckage.

Passengers in the duck boat that was unable to move apparently had just seconds to grab their life jackets and jump for their lives.

According to police, the majority of passengers did jump off the amphibious vehicle.

"There were some pictures that we had (that we turned over) that were taken by a citizen that was on-shore here that actually shows, it shows the impact. You do see some graphics of people jumping off," a police investigator told the media.

Fox 29 News has obtained one such photo from a source.

The Coast Guard says passengers were not required to wear life vests, but it was necessary for them to have easy access to the vests.

The 35 who were rescued were pulled out of the water by passing boats, Good Samaritans, and first-responders, including Navy sailors from Special Boat Team 20.

The 12 crewmen of the "special warfare combatant-craft" just happened to be in Philadelphia to attend community relations functions and were preparing to get underway to Schuylkill Banks to dedicate "Navy SEAL Grove," as well as provide boat tours for the public.

Police updated Thursday morning that 11 of the passengers were taken to hospitals. Most were treated and released, but two were admitted -- one for a broken jaw, and the second for some type of trauma or shock. It's not clear if those last two have been released.

Rescue boats have been searching all night and all day between the Ben Franklin and Walt Whitman bridges for any sign of the missing tourists. They have pulled some life preservers from the water.

Shipping channels closed Wednesday along that segment of the river have reopened, but ships are being escorted through the area.

Police said a second dive to the submerged duck boat was attempted overnight, but divers could not reach the bottom because of the swift current and poor visibility.

The Coast Guard's Gatlin said they will not be diving Thursday morning: "After talking to the Philadelphia police, because of the murkiness of the water and the visibility underneath the water, the dive teams will not be going back down this morning."

Sr. Chief Charles Weaver, who made Wednesday's dive, said: "The vehicle is laying upright on its wheels. There could be bodies inside, we're not sure. It is an open vessel. With the currents being what they are ... if it went down with bodies inside, those bodies very well could have been washed out of the vessel."

The boat is expected to be pulled out of the river sometime soon. The Coast Guard said the duck boat company must first submit a salvage plan for its review.

Finding that boat should give the NTSB some answers, and we hope to get some of them when investigators hold a news conference later on Thursday.

"Ride the Ducks" issued a statement on its website Thursday morning and suspended operations nationwide. The company based in Norcross, Ga., operates amphibious vehicle tours in five other cities: San Francisco, Seattle, Atlanta, Newport, R.I., and Branson, Mo.

"Our thoughts and prayers are with our Philadelphia tour guests, crew members and their families," the statement reads. "We are attending to their needs first. In the interim, we have voluntarily suspended our Ride The Ducks operations nationwide. If you already have a reservation, you can receive a full refund or reschedule for a future date. We will resume operations shortly."

• Fox 29 News Philadelphia