SAN DIEGO — Two men were charged Wednesday with a slate of narcotics and weapons charges in connection with a drug-lab explosion that set a northern San Diego County home ablaze last spring.

Gregory Allen Amos, 23, and 34-year-old Christopher Paul Hernandez allegedly were using butane to extract hash oil from marijuana in a house in the 1200 block of Barbara Drive in Vista when the blast occurred about 10:45 a.m. March 27, according to a federal criminal complaint.

Deputies and firefighters arrived to find a glass door blown out on a second-floor balcony of the burning residence and dozens of cans of butane strewn on the driveway, the court document states.

Inside the damaged home, authorities found the remnants of a butane hash-oil laboratory and related items, including pounds of marijuana, hundreds of cans of butane and glass tubes. Agents also seized about a pound of cocaine and three guns, including a 5.56-mm rifle and a 9-mm semiautomatic pistol.

Operating a butane hash-oil lab is an illegal and highly dangerous way extract THC, the principal psychoactive found in marijuana plants.

Since January, San Diego-area law enforcement personnel have dealt with at least 17 such illicit facilities, three of which generated fires or explosions, according to federal officials.

Using butane to obtain hash oil — which contains extremely high levels of THC and can be up to four times more potent than high-grade marijuana — often results in the highly flammable gas evaporating and collecting on the floor, then accumulating to explosive levels.

“BHO manufacturing poses an enormous threat to human life,” San Diego-area U.S. Attorney Adam Braverman said. “No one is safe — not those involved in the illegal (process) themselves, not those who happen to be living or visiting nearby, not first responders.”

Amos, a Vista resident, and Hernandez, of San Diego, are scheduled to be arraigned in the case Friday afternoon.