A 15-year-old Santa Rosa boy was arrested on suspicion of making hash oil in a shed in his family's backyard, Santa Rosa police said.

Police began watching the Bennett Valley residence after 2 p.m. Friday when they received a tip that there was a drug lab at the home, Sgt. Michael Chad Heiser said.

Police searched the residence and found a makeshift lab in a backyard shed that used highly flammable butane gas to make hash oil, a process that has caused several recent explosions on the North Coast.

"Anytime you have butane extraction for the manufacturing of concentrated cannabis, it's a dangerous setup," Heiser said. "There is no safe way to do that."

Police also found 43 pounds of loose-leaf marijuana and seven grams of concentrated cannabis, Heiser said.

The boy, who was not identified because of his age, was arrested and booked into the Sonoma County Juvenile Hall on suspicion of manufacturing a controlled substance, possession of concentrated cannabis and possession of marijuana for sale, Heiser said.