ANCHORAGE, Alaska (AP) _ Four boys in a pickup truck and a tour bus driver were killed in a fiery head-on crash south of Denali National Park. The tourists on the bus escaped without serious injury.

Alaska state troopers said the bus operated by Alaska Sightseeing-Cruise West was southbound with 15 people on board when it collided with a northbound pickup truck Wednesday in a no-passing zone on the Parks Highway.

The truck came to rest under the bus and set it on fire, leaving the bus a charred skeleton. Passers-by tried in vain to put out the fire and rescue the bus driver, Michael Rogers, 29.

''He kept saying, 'Help me 3/8' I was standing out there watching, but there was nothing we could do,'' one of the passers-by, Army Sgt. David Lancaster, told the Anchorage Daily News.

He said he and a friend tried to pull Rogers out, undoing his seat belt. But Rogers' foot was jammed in and he was stuck.

''All the way home I've been thinking about that driver,'' Lancaster said.

John Kreilcamp, the tour bus sales director in Anchorage, said the 40-foot coach was on a return trip to Anchorage when it crashed. Kreilcamp said Rogers knew so much, coworkers called him ''The Anchorage Encyclopedia.''

The four victims in the truck were identified as Stephen Smith, 16, of Willow; Simon Lee, 15, and twin brother Graham of Trapper Creek; and Jason Link, 12, of Trapper Creek. It wasn't known which was driving or whether they died in the crash or from the fire.

Two tourists were admitted to hospitals for treatment of cuts and bruises, while at least 11 others were treated and released.