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DENVER — One person was killed and three others were critically injured in a fiery crash on Interstate 25 north of downtown on Thursday morning, the Denver Police Department said.

The crash involved a dump truck and a Jeep SUV in the northbound lanes near East 52nd Avenue, forcing the closure of the interstate.

Police said the vehicles were traveling next to each other in the far right lanes when for unknown reasons they collided. The collision pushed the Jeep on top of a Jersey barrier next to the shoulder where it caught fire, police said.

“Just a big boom,” said Michael Coleman, who heard the crash before he saw it. “You could hear it hit the back of something and then the brakes.”

He ran from his backyard just off I-25 and 52nd Avenue and saw large flames engulfing both vehicles.

“When it all came to a halt, all of it was a burning inferno,” he said. “Everybody just stopped, jumped out of their vehicles and ran and helped these people get out. Amazing anybody even survived.”

The weight of the truck pushed the Jeep on top of the barrier.

“After it hit it, it bumped it up on the wall and it was so much weight, he couldn’t stop. So he drug that car on top,” Coleman said.

Witnesses said a badly burned woman on the passenger side of the Jeep rolled down the short embankment off the highway.

“The lady either fell out of there, over this wall, she was rolling down screaming, help, help, help and then the other people that was on the highway were pulling the driver out of this truck and I guess two other people,” Coleman said.

Two others in the Jeep were pulled out by people stopping on the highway to help. Police said a fourth person in the Jeep was pronounced dead at the scene. The driver of the dump truck escaped without physical injury.

“I just feel sorry for their family and especially before Memorial Day. I just hate seeing it happen. I do,” Coleman said.

Police are trying to determine who or what caused the collision.

“We do know that they collided. Why is unclear. Somebody obviously left their lane of travel we are still working that evidence,” Sgt. Mike Farr said.

Firefighters put out the flames in both vehicles as well as a small grass fire that was started from the crash.

Northbound Interstate 25 was closed for nearly an hour between East 42nd and East 58th avenues as crews worked to put out the fire.

Two of the five lanes of traffic reopened about 11:20 a.m., but there were long delays in the area. The full interstate didn’t reopen until during the evening commute.