CHATTAROY, Wash. -

An explosion, a fire, and a criminal investigation. Two people were badly burned after fire destroyed a mobile home in Chattaroy around 5:30 p.m. Wednesday near the 3200 block of East Chattaroy Road.

Major Crime's detectives are investigating the incident as a domestic violence assault. They say it appears the man inside released propane gas, then ignited it while another woman was inside.

Neighbors say it started with an explosion felt blocks away.

"I felt my house shake like an earthquake, I didn't know, I thought something had run into my house," Tammy Millspaugh said.

Spokane County Fire District 4 is located less than a quarter-mile away, but the fire engine was at another fire at the time. An off-duty firefighter on his way into work saw the smoke and called other firefighters back. He then took the reserve engine to the location on East Chattaroy Road and started fighting the fire with several other firefighters. District Chief Howard Johnson said when he arrived five minutes later, the home was already destroyed.

"We got units on scene, and we were able to do a pretty good knockdown initially, and as we were fighting the fire we encountered that there were two people who had been burned," he said.

The man and woman inside the mobile home when it exploded were outside when firefighters arrived. Deanna Moore ran to help the woman as another neighbor was hosing the man down. They were both badly burned.

"I just told her to calm down, that everything was going to be ok, and not to worry that the paramedics were on their way, and that she was going to be ok, and that I'd stay with her," Moore said.

The man and woman were transported to Spokane, and then to Harborview Medical Center in Seattle by MedStar and Life Flight. He is in critical condition; the woman is in serious condition. Neighbors believe the two were separated or divorced.

The scene is being guarded by Spokane County Sheriff's Deputies, so Major Crime's detectives can come back Thursday morning and continue their investigation in daylight hours.