BILLINGS - A trailer hauled by a FedEx truck caught fire and exploded on Interstate 94 east of Billings on Wednesday, triggering a grass fire and an interstate closure, officials said.

The Montana Department of Transportation website states that a FedEx truck hauling hazardous materials caught fire in the westbound lane near mile marker nine of I-94 east of Billings at 3:53 p.m.

The FedEx truck was towing three trailers, and the driver had a brake system malfunction, which caused the fire, said Montana Highway Patrol Trooper Joshua French. Smoke and flames grew in the rearmost trailer.

Another driver flagged down the FedEx driver, who stopped and tried to extinguish the flames, French said. When that didn't work, the driver disconnected the trailer and moved the truck away.

The driver of the FedEx vehicle was "OK," said Worden Volunteer Fire Department Chief Lance Taylor.

The trailer, holding six one-pound containers of organic peroxide, exploded three times before Taylor and his firefighters arrived at the scene, Taylor said.

The explosions sparked a grass fire, which grew after another explosion sent a burning tire 10 feet into a field of dry grass, according to Taylor. The five-acre grass fire was extinguished around 5:30, Taylor said.

A HAZMAT team handled further cleanup after the fire, he said.

The Yellowstone County Sheriff's Office shut down the interstate around the area and traffic was diverted, said Yellowstone County Disaster and Emergency Services director Brad Shoemaker.

The Worden Fire Department, Shepherd Volunteer Fire Department and the Department of Natural Resources and Conservation responded to the scene, Shoemaker said.