A pickup left the Seward Highway and flipped early Thursday morning, breaking through the roadside ice and trapping the two occupants underwater, according to troopers and firefighters.

The bodies of a man and a woman, still seat-belted in the cab of the 2000 Ford F-350, were found by rescuers after the crash was reported at 5:05 a.m. They had to be extricated from the vehicle.

Authorities later identified the driver as Carolyn Crane, 26, and the passenger as John Cunningham II, 38. Both are residents of Sterling.

Alaska State Troopers say alcohol and speed appear to be the main factors in the wreck, which occurred in decent road conditions on a clear morning. There were apparently no witnesses to the crash.

Evidence at the scene indicated the pickup had been traveling toward Seward on the highway when the driver apparently lost control, said troopers Sgt. Eugene Fowler, with the Bureau of Highway Patrol. There was no indication another vehicle was involved, he said.

"It slid across the roadway, across the northbound lanes, into the ditch," Fowler said. "Along that side of the road there's water there. It hit the water, rolled several times and came to rest upside down."

It wasn't known how long the vehicle had been there by the time another driver reported it submerged in about 4 feet of water near Mile 76.1, a straight, flat stretch of road about a mile north of where the ascent begins to Turnagain Pass.

The truck's headlights were still on in the dark, but only its wheels and undercarriage were above water where it sat on the south side of the road, said Richard Parry, assistant chief of the Girdwood Fire Department.

Firefighters arriving on scene waded out to the wreck and hooked a winch to it, allowing them to turn it on its side, he said.

"The entire passenger compartment was submerged and full of ice and snow and water," Parry said. "So it was clearly not a survivable incident at that point."

The tail end of the vehicle was only about 5 feet out into the water, but the vehicle was perpendicular to the road, he said. A wrecker was called in to pull it out.

Firefighters, medics and divers from the Anchorage Fire Department also headed to the area to search the water in the aftermath of the wreck, AFD spokeswoman Jen Collins said.

"Our dive team went under the ice to ensure that there was nobody else in the accident," she said. "We didn't find anyone."

There have so far been eight fatal accidents resulting in 11 deaths on the Seward Highway this year, according to the Alaska Highway Safety Office. All but the two most recent took place between May and August.

The last fatal crash, on Nov. 5, took place at Potter Marsh, where an alleged drunken driver, Lori Phillips, 55, crossed the center line in an SUV and collided head-on with a Toyota sedan. That vehicle's driver, Louis Clement, 23, was killed and his fiancee, Joyua Stovall, 29, was critically injured.