MESA, Ariz. — A dump truck barreled across a Mesa freeway median barrier, collided with at least two other vehicles and caught fire, resulting in a seven-vehicle wreck that somehow didn’t result in any serious injuries, authorities said.

The people in the seven vehicles damaged by collisions, the fire or flying debris had only bumps and bruises, said Cap. Damon Cecil, a state Department of Public Safety spokesman. “It was definitely a blessing.”

Before being extinguished, the fire burning fuel from the truck’s side tanks sent flames and black smoke high above the dump truck. Its rear end was heavily damaged by the fire, as were a SUV and a pickup next to it.

Two sets of axles broke loose from the wreckage. The median wall was also damaged, with pieces of concrete deposited on the pavement.

The wreck closed the freeway’s eastbound lanes starting at about 6 a.m., resulting in long delays during the morning commute.

The freeway was reopened after tow trucks and other equipment removed the wrecked vehicles and debris.

Cecil said the DPS was investigating why the dump truck crossed the median.