Emergency management officials predicted several fatalities in a bridge collapse over the Arkansas River Sunday, estimating that about five to 12 victims were trapped in vehicles underwater and were likely dead.

The 500-foot section of roadway collapsed when a barge hit the interstate bridge during a storm, sending about a dozen vehicles plunging into the water, authorities said.

Crews pulled two cars and a motor home from the water Sunday evening and found three bodies, said Lt. Chris West, a spokesman for the Oklahoma Highway Patrol.

Officials expected to find a total of five to 12 bodies in the submerged vehicles but said it would likely be Monday or Tuesday before all the victims could be removed.

Cranes were brought in to stabilize the two bridge sections that slanted from Interstate 40 into the river as divers struggled Sunday afternoon against a strong current in the murky, 11-foot-deep water, said Rebecca Smith, a spokeswoman for Muskogee County Emergency Management Services.

At least five people were being treated at hospitals, including some who had been rescued from the river as boatmen alerted authorities to the collapse of the section of the 1,988-foot bridge shortly before 8 a.m.

Gov. Frank Keating, who visited the area Sunday afternoon, said the captain of the barge may have had a seizure and blacked out just before the barge rammed a column supporting the bridge.

He said the captain, identified as Joe Dedmon, of Florence, Miss., was being examined at an area hospital.

"One of the fire officials asked two tug mates and they said it was a seizure or a blackout and the captain hit the bridge," Keating said. "There was a number of fishermen down there who saw it happen. They said it veered right into the piling and here came the road."

Preliminary tests found that Dedmon did not have alcohol or drugs in his system, said Joel Henderson, an attorney for Magnolia Marine Transport Co., which owns the towboat. Henderson said the Coast Guard and FBI had spoken with Dedmon.

It wasn't clear whether the storm and fast-moving river water contributed to the crash.

"The loss of life is something that is unbearable for all of us because these are people traveling on Memorial Day from all over the country," the governor said. "It is a sad day for all of us."

Josef Blann, a diver with the Marine Corps Reserve, said authorities believed 15 vehicles went into the river, including 12 cars, two tractor-trailer rigs and a horse trailer. Keating said the total number could be as low at nine.

Three dead horses were pulled out of the water, West said. The recovery effort was suspended Sunday night and will resume at daylight Monday, he said.

Two bridge pilings in the water were knocked down, and one piling on the bank was tilted. The damaged pilings were all on the west end of the bridge.

At nearby Webbers Falls, officials set up a morgue inside city hall, and a funeral home had become a meeting place for families searching for relatives who might have been on the bridge.

Sunday afternoon, rescue crews in boats moved along the river's surface, picking up floating pieces of car seats, clothing and diapers. Huge slabs of concrete where the west side of the bridge gave way slumped in the water close to the river's edge.

A pickup truck rested on top of one section of collapsed concrete at the west end of the bridge, which rested on the embankment. The driver had slammed on his brakes when he noticed the bridge was gone, authorities said.

Both eastbound and westbound sections of the Interstate 40 bridge, about 75 feet above the Arkansas River, collapsed, pinning the barge beneath it.

Shane Guthrie, personnel manager for Magnolia Marine Transport in Vicksburg, Miss., said the company's 104-foot-long towboat, the Robert Y. Love, was pushing two barges when the accident occurred. None of the seven crew members was injured, officials said.

"They just got hold of the bridge span there somehow," Guthrie said. "We're still investigating what caused the accident."

The National Transportation Safety Board sent a team to investigate.

The bridge was about 100 miles east of Oklahoma City and about 35 miles west of the Arkansas line.

Four people injured in the collapse were being treated Sunday at Muskogee Regional Hospital, all in stable condition, administrator Ched Wetz said. A fifth person was taken to Sequoyah Memorial Hospital with non-life-threatening injuries.

"One gentleman said he was driving and all of a sudden there was nothing under him," Wetz said. "He doesn't remember how he got out of his vehicle. He probably swam out, but he simply doesn't remember."

Interstate 40 normally has heavy traffic through the area, said Highway Patrol Sgt. Jarrett Johnson.

"There are probably thousands of cars that travel over this bridge every day," he said. "It's the main interstate that travels east and west through the state of Oklahoma."

Keating said it likely would take six months to rebuild the bridge.

In September 2001, a tug boat and barge struck the Queen Isabella Causeway in Port Isabel, Texas, causing a midsection of the bridge to tumble into the bay 80 feet below. Eight people died after motorists drove into the hole.

In May 1980, a freighter sheared a bridge support in Florida's Tampa Bay, dropping a 1,400-foot section of concrete roadway during morning rush hour. Seven vehicles, including a bus with 26 aboard, fell 150 feet into the water. Thirty-five people died.

The Associated Press contributed to this report.