2 Tanks Had Been Stolen, Police Say : Theft: The cylinders of nitrous oxide used by three men who died were believed taken from Holy Cross Medical Center.

Two tanks of nitrous oxide, the so-called laughing gas linked to the accidental deaths of three young men last week in Chatsworth, were stolen a month earlier from Holy Cross Medical Center, where one of the victims formerly worked, police said Tuesday.

The two 80-pound tanks found with the victims Friday did not carry individual serial numbers but by asking area hospitals to inventory their cylinders, police were able to determine that the tanks were the two stolen Feb. 19 from the Mission Hills hospital, investigators said.

The men were found dead of apparent asphyxiation in the cab of a pickup truck parked on Topanga Canyon Boulevard. The valve of one of the cylinders, which was in the truck cab, was open and still emitting gas when police found the bodies.

Autopsy results are not yet complete.

The victims were identified as Michael Cook, 23, of Sherman Oaks; Matthew Champy, 21, of Woodland Hills, and Richard Dellavechia, 20, of Sepulveda. All three were known by friends to attend “underground raves” where nitrous oxide is often inhaled by young party-goers.

Holy Cross officials said Cook worked as a maintenance worker at the hospital until October and would have had access to a key to the storage area where the tanks were kept. Officials said an investigation of the theft, which occurred four months after Cook left the job, determined that the thief had used a key to steal the tanks.

Los Angeles Police Detective John Cameron said there is no evidence specifically linking Cook to the thefts. He said determining where the tanks came from closes the investigation.

“I’m satisfied we know where the tanks came from,” Cameron said. “It’s kind of hard to say exactly who took them, whether it was him or someone else. But it was someone with knowledge of where they were and how to get them.”