SPARKS, Nev. » Nevada officials said Saturday that investigators had confirmed six deaths after a semi-truck slammed into an Amtrak train a day earlier on a rural Nevada highway.

The Churchill County Sheriff’s Office said in a release late Saturday that officials were working to confirm the victims’ identities and notify family members.

Amtrak’s California Zephyr was en route from Chicago to Emeryville, Calif., with some 200 passengers and 14 crew members when the accident occurred late Friday morning about 300 miles east of its destination.

Nevada Highway Patrol Trooper Dan Lopez said that the truck driver and an Amtrak conductor were among the confirmed dead in the crash. About 20 people were injured and able to escape.

Earl Weener (WAY’-nur), of the National Transportation Safety Board, also said late Saturday at a news conference in Spark, Nev., that about 28 people remained unaccounted for, but he added that some passengers may have gotten off the train before the accident or been able to leave the scene and not informed authorities.

Sixteen National Transportation Safety Board investigators took over at the scene Saturday and are expected to take up to a year to pinpoint the cause of the crash.

Lopez said the investigation would focus on the truck driver, whose rig crashed through a crossing gate before plowing into the Amtrak car. A witness told authorities that the crossing gates and warning signals were working at the time.

"That’s what everybody wants to know. Why did the truck collide with the train?" Lopez said. "Unfortunately, since he was pronounced dead, he’s the only one who can tell us that prior to the investigation."

Following medical evaluations or treatment, most passengers continued their travel west on chartered buses or chose to make their own arrangements, Amtrak said in a news release.

Eugene Rheault of Manchester, N.H., was on a trip from Yellowstone National Park to San Francisco when the accident occurred.

"My wife and I were playing cards in the observation deck when there was a big bang and an explosion and an unbelievable amount of fire went by the window," Rheault told the Reno Gazette-Journal. "It scared the living daylights out of me."

Alex Graham, 18, of Fort Wayne, Ind., was reading a book while on a trip to the West Coast with his mother when the Amtrak was hit.

"And then a wall of fire went by the window," he said. "I could feel the heat instantly."

Passengers have provided conflicting accounts of which car was hit, ranging from the second to fourth car.

The collision was on a portion of tracks that cross U.S. 95 about three miles south of Interstate 80.

The driver was the only occupant of the semi, which was hauling two empty gravel trailers.