BOISE, Idaho (AP) — Authorities have identified two people killed when a gas station exploded and started a fire in a remote Idaho town last week.

The Clearwater County Sheriff’s Office said Brandon Cook, 53, of Orofino and Wesley Lineberry, 62, of Pierce were both killed in the explosion at the Atkinson Distributing station in Cardiff on Sept. 11.

Two others were badly burned in the explosion and subsequent fire, and they remained hospitalized on Wednesday. Separate GoFundMe pages identified the injured as fuel tanker driver Donny Billeter and gas station attendant Roxann Hubbs.

A fuel tanker semi truck was in the process of filling the above-ground tanks at the station when the explosion happened just after 3 p.m., said Idaho State Fire Marshal Knute Sandahl. The blast destroyed the tanker and sent debris including truck parts, piping, pieces of the tank and chunks from the gas station building flying across an area about the size of a city block, Sandahl said.

Both the tanker truck driver and the gas station attendant were near the truck when the explosion occurred. The bodies of Lineberry and Cook were found just outside the gas station, but investigators have not yet confirmed if they were inside or outside the building when the disaster began, Sandahl said.

RELATED COVERAGE Man charged with killing 4 university students in Idaho is jailed in Boise after his trial is moved Idaho’s high court moves the trial for the killing of 4 university students to Boise Explosion at an Idaho gas station leaves two critically injured and others presumed dead

It’s not yet clear what caused the explosion, Sandahl said, and the National Transportation Safety Board and the Occupational Safety and Health Administration are assisting in the investigation.

“We’re digging deep and it’s just going to take some time,” said Sandahl. “I’m hoping we’ll have something a little bit more definitive to release in October sometime.”

Some nearby buildings were also damaged by the explosion and fire, and the remaining fuel at the site has been an obstacle for investigators. A regional hazardous materials response team was called in to help mitigate the danger.

Gas station explosions are rare, Sandahl said.

“In my 19 years of being a state fire marshal here in Idaho, this is the first incident I’m aware of,” he said.

Offloading — the process of moving fuel from a tanker truck to a station’s storage tanks — increases the risk somewhat but is still typically a very safe process because the drivers follow specific procedures, he said.

“Quite honestly, I think the most dangerous thing is fueling up your vehicle while smoking or filling plastic gas cans in the back of your pickup truck,” which increases the risk of sparks from static electricity, Sandahl said. “As we know from high school chemistry, it’s actually the fumes that are volatile, and if there is a spark introduced, it can cause a problem.”