A former Los Angeles police officer who was running a hash oil lab out of a house in Lake Elsinore was sentenced Monday to five years in prison, officials said.

Authorities began investigating Joseph Jay Spadafore, 64, after an explosion at the makeshift lab revealed that he’d been extracting tetrahydrocannabinol, or THC, from marijuana plants using butane, a highly flammable gas, in a volatile process to make hash oil, according to the U.S. attorney’s office.

Neighbors reported the explosion just before midnight on Nov. 3, and firefighters found the garage engulfed in flames. Spadafore — who was an LAPD officer from 1976 to 1991 — was the only one living there, though the homeowner thought the place had been rented to someone else, officials said.

Spadafore told a fire captain that the blaze may have ignited because he’d been draining gas from his motorcycle in the garage, according to a sentencing memo filed by prosecutors.

But inside the home, firefighters found potentially hazardous lab equipment and flammable chemicals in almost every room. Authorities found between $300,000 and $500,000 worth of drugs.

Authorities seized at least 22 propane tanks, dozens of soda kegs and other large containers filled with extracted THC, jars of THC powder and trash bags filled with marijuana, officials said. They found more than 28 liters of hash oil in the home, which authorities said had been converted almost entirely into a drug lab.

Two guns were also found: one, loaded, under Spadafore’s pillow and another between the mattress and the box spring, prosecutors said in the filing.

In March, a jury convicted Spadafore of one count of maintaining a drug-involved premises. The jury found him not guilty of possessing firearms in furtherance of a drug trafficking crime, and there was a mistrial on two other counts: possession with intent to distribute hashish oil and endangering human lives while manufacturing controlled substances.

Prosecutors had argued that a 6 ½-year sentence was appropriate because of the risk the lab posed to the neighborhood. They said it was necessary to deter others from manufacturing drugs, especially in residential neighborhoods. They also cited Spadafore’s conduct when firefighters arrived, saying the former cop “did nothing to warn them” of the dangers inside the home.

At the sentencing, Judge John F. Walter indicated that Spadafore’s lack of remorse for not warning first responders about the hazards played into the sentence, the U.S. attorney’s office said.

Walter also rejected Spadafore’s argument that he was “crashing” at the house because he needed a place to sleep, finding that the defendant was involved in the drug manufacturing and kept the guns to protect himself and the drugs, officials said.

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