Eight contract firefighters who had spent two weeks fighting an Idaho wildfire (search) were killed on their way home when their van collided with a tractor-trailer and exploded into flames.

The 11-passenger van apparently tried to pass another truck on a curve and crossed the double-yellow line before it collided head-on with the truck Sunday morning, Malheur County Undersheriff Brian Wolfe said.

It took more than seven hours for the section of remote eastern Oregon highway to reopen, once authorities recovered the bodies and highway crews shoveled ash and debris onto trucks.

The wreckage of the van and the semi were almost indistinguishable. The charred frame of the van was torn in two. The cab of the semi was demolished but the diesel exhaust stack remained erect.

The firefighters, all men under the age of 23, worked for First Strike Environmental (search), a Roseburg-based contract firefighting company. Their names were not expected to be released until Monday because authorities were still trying to reach their relatives.

"I extend my wholehearted sorrow and sympathy to the families who lost their sons today," First Strike president Robert Krueger said in a statement. "These were all fine young men who had worked together for two years. They were closer than most and the hole they leave is enormous."

First Strike spokeswoman Leslie Habetler said six of the men were from Douglas County, the southwestern Oregon county that includes Roseburg, and two were from the Portland area.

Roseburg Mayor Larry Rich said he was in shock when he learned about the crash.

The two occupants of the Swift Co. tractor-trailer (search) were able to free themselves and were taken to an Ontario hospital with dislocations and burns, Wolfe said. Their names and conditions were not available Sunday night, but Wolfe said their injuries were not life-threatening.

The crash, about 15 miles west of Vale, was under investigation.

The van had been traveling with another First Strike van and a truck. Both those vehicles were about six miles ahead and did not see the crash, Habetler said.

First Strike has been in business for more than 15 years and keeps about 200 firefighters on call during forest fire season. More than 90 percent of the privately contracted fire crews in the United States are based in Oregon.

Fire coordinators said the van that was struck was coming back from a wildfire in the Boise National Forest (search) about 25 miles northeast of the town of Cascade, Idaho.

Before Sunday, 19 firefighters assigned to wildfires had died on duty this year, according to Tracey Powers, spokeswoman for the National Interagency Fire Center in Boise. Nine died in motor vehicle or aviation accidents, three died in fires, six died of illnesses and one died when a tree fell on his tent.