WEBBERS FALLS, Okla. ? Rescuers hoisted two vehicles with four bodies inside on Tuesday from the murky Arkansas River, bringing the death toll from the collapse of an interstate bridge to 13.

Lightning, rain and rising waters hampered the rescuers, who picked their way through the muddy water searching for an unknown number of people still missing after an out-of-control barge hit the Interstate 40 bridge and knocked out a 500-foot section of highway.

Automobiles, a horse trailer and other material pulled from the Arkansas River sits on the bank near the site of the Interstate 40 bridge collapse near Webbers Falls, Okla. The death toll from Sunday's collapse rose to 13 Tuesday.

“We’re determined because we know there’s family members out there wondering if one of their own is in here,” said Dennis Splawn, a diver with the Oklahoma Highway Patrol.

The bodies of seven women and six men have been recovered from the waters below the ridge, said highway patrol Lt. Chris West. With the help of sonar, a crane had hoisted 10 vehicles from the pile of mangled concrete and twisted steel.

A champion horse trainer and a police detective were among those killed, authorities said.

About 10 families of people trapped in cars at the bottom of the river waited at the Webbers Falls City Hall for news. About a dozen vehicles plummeted into the water Sunday morning after the barge hit.

Earlier Tuesday, an investigator said towboat crew members’ accounts support the towboat company’s contention that the pilot had blacked out.

George Black of the National Transportation Safety Board said a crewman who visited with Capt. Joe Dedmon five to 10 minutes before the accident said everything seemed normal.

Others who were not with the captain said they heard no alarm or change in the sound of the engine that would indicate he was trying to avoid a crash, Black said.

Dedmon, who tested negative for drugs and alcohol, was to be interviewed by NTSB investigators. His brother, Ray Dedmon of Raymond, Miss., said the captain has never had seizures or similar medical conditions to cause him to pass out.

Gail Shanahan, 49, was returning to Texas with another horse trainer, Maggie Green, when their truck and a trailer hauling four horses plunged off the bridge, family members said. Searchers have pulled three horses out of the river. A former Texas Youth Rodeo champion, Shanahan trained horses for barrel racing.

Norman police Det. Wayne Martin and his wife, Susan, were heading to Arkansas for a family reunion Sunday morning, but they never arrived.

“We are pretty well resolved to the facts,” said Norman Police Lt. Glenn Dobry. “It’s extremely tough.”

Investigators were trying to determine whether there was anything wrong with the 35-year-old bridge that might have caused it to collapse.

Steve Tipton, a University of Tulsa engineering professor, said the impact of the collision would have been roughly equivalent to 62 2,000-pound cars slamming into the structure simultaneously at 60 mph.

“It would look deceivingly slow, like you might be able to reach out and stop it yourself,” he said. “But it actually would have had a tremendous amount of power to it.”