"I could feel it lean to the right . . . ; the next thing I knew I was being slammed" against the cab, he said. That's when he received most of his injuries, which were cuts and scrapes.

He found Stewart, whom he calls a friend, and helped get him out of the seatbelt. Stewart ran from the truck and Lysfjord followed.

Lysfjord estimates that about 3 minutes passed between the rollover and explosion. He was about 75 yards away. He was in and out of consciousness in the canyon but said he tried his best to warn people to get away, maybe at the expense of his own safety.

"I spent way too much time trying to get people to move. They didn't move fast enough," he said. "That's hard to do when people don't listen. They're just curious, I guess."

Mapleton resident J.D. Herbert, who was treated for injuries at UVRMC, was traveling through the canyon and was thrown off his motorcycle by the explosion. He tried to seek shelter behind a minivan.

"The mom was screaming and her kids were crying," Herbert said. "Shrapnel (was) hitting the forest and crackling like bacon."

In all, eight people sought treatment at the Provo hospital, said Janet Frank, spokeswoman for UVRMC.

"The blast was hard enough to blow out windows," Utah Highway Patrol Sgt. Al Christianson said. "That's pretty significant."

He compared the blast to a war-zone-type incident, and the site was still being monitored for undetonated explosives into the evening.

The explosive devices that were in the truck — small orange tubes nearly 10 inches long — are used in seismic exploration and are normally safe. However, the intense heat of the fire was too much, and all but 60 pounds exploded, said UHP Lt. Kenneth B. Peay.

The truck was following federal regulations, according to the Utah Department of Transportation and company officials.

"It is up to the United States Department of Transportation to regulate and issue permits, but as far as we know, this truck had the necessary permits to carry whatever it was carrying," said Nile Easton, spokesman for the UDOT. He said rules and regulations pertaining to the transport of hazardous materials are left up to the federal government to ensure uniformity across the states where big rigs travel.

Because of the blast, the highway is impassible, and nearby railroad tracks were bent like pipe cleaners. There is no timeline yet as to when the tracks will be ready again. The line is used by Union Pacific Railroad, Amtrak and for coal transportation.

Amtrak officials said they are holding a passenger train in Grand Junction, Colo., that would have had to pass through Spanish Fork Canyon.