The three people who were badly burned after an RV burst into flames outside a Delta gas station Saturday were siphoning fuel through a trap door in the vehicle, according to police.

Acting Sgt. Sarah Swallow said the trio parked the motorhome above the Petro Canada’s underground holding tank around 3 a.m. then lowered a hose through a hole in the floor.

“They’d basically set up a bit of a mini mobile gas theft station,” Swallow said. “They put a hose right down into the main fuel tanks and were syphoning as much gas as they could prior to the whole thing blowing up.”

Investigators haven’t determined how the fire started but believe hundreds of litres of gasoline had already been transferred into a large plastic storage tank in the RV when it ignited.

“It could be anything from a cigarette to electronic ignitions in stoves in the motorhome or some sort of malfunction in whatever syphoning equipment,” Swallow said.

Two men were found at the scene and taken to hospital, where they remained in critical, but stable condition Monday. A woman was also seen fleeing the area with burns to her head but police located her Saturday afternoon in New Westminster.

All three face several charges, including theft over $5,000.

Gas theft has increasingly been a problem for police across Metro Vancouver but Swallow said this case is the first she’s seen of thieves attempting to access a holding tank directly.

“The difficulty with this type of theft is they’re able to hit gas stations after hours when the gas stations are closed,” she said. “Our advice to people would be to have good surveillance, good security.”

The theft is also less obvious because thieves don’t have to park their vehicles near the pumps. Police are concerned that if a similar fire breaks out, bystanders could run over to help without realizing the danger they’re in.

“Most Good Samaritans will see a fire like this and go in and help, understandably,” Swallow said.

Investigators haven’t confirmed where the stolen gas was intended to be sold, but said it sometimes is advertised on Craigslist.