Multiple people died Thursday when a semitrailer plowed into stationary traffic that resulted in explosions and flames on a Colorado freeway, authorities said.

The fiery crash occurred just before 5 p.m. in the Denver suburb of Lakewood when a truck driver lost control while traveling east on Interstate 70, according to a preliminary investigation. The collision started a chain reaction and a diesel fuel spill, Lakewood police spokesman Ty Countryman told the Denver Post.

Several people died Thursday in a fiery crash involving multiple vehicles and three semitrailers.  

Several people died Thursday in a fiery crash involving multiple vehicles and three semitrailers.  
(West Metro Fire Rescue)

“This is looking to be one of the worst accidents we’ve had here in Lakewood,” he said.

The cause of the crash was under investigation. Countryman called it “one of the worst accidents” his department has had in the area.

The driver of the runaway truck survived. At least one truck was carrying lumber, another was hauling gravel and the third may have been carrying mattresses, KDVR-TV reported.

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Lakewood police tweeted there were multiple fatalities but did not give a specific number. Six people were taken to a hospital. Their conditions were not released, according to the paper. A press conference will be held at 7 a.m. local time.

Lanes in both directions were closed and expected to remain so into Friday morning.

12 cars and three semis were allegedly involved in the incident, police said, according to the Denver Post.