Asian Gang Task Force detectives served five search warrants and dismantled what they consider a sophisticated growing operation.
Authorities confiscated a total of seven handguns, three assault weapons, a rifle and a shotgun during the raids, which were culminations of a 2-month-long investigation.
They also detained seven Chinese immigrants as well as the operation's alleged ring leader, 49-year-old Minh Luu of San Gabriel.
Investigators said the suspects lived in single-story homes, and almost every room was filled wall-to-wall with marijuana plants, growing under lamps. Three of the four homes were about 2,000 square feet.
Investigators say they believe one of the homes served as a sort of headquarters for the pot operation.
The sheriff's department said the four homegrown operations were going on in neighborhoods that were not seedy or plagued by crime.
"Typically, you wouldn't expect these things in your neighborhood. That's why it's up to the public to inform us if they see anything suspicious, because otherwise a lot of the times, it takes a while for these investigations to come up," said L.A. County Sheriff's Department Deputy Benjamin Grubb.
Neighbors were stunned by the raid on Fairview Avenue in Pasadena. Resident Brittany Johnston thought the house was vacant.
"There was a 'for sale' sign up for the longest time on the house, and then one day, it was just down, and I didn't even know anyone was living there," said Johnston.
Some neighbors say they saw young men, perhaps teenagers, coming and going from the home late at night, and figured they were new renters.
"There are a lot of elderly people, no big parties, commotion, nothing on this street. For something like that, yeah, it's a big deal for this area," said Johnston.
The sheriff's department advised neighbors to look for suspicious activity such as a lot of people coming and going during the night and fertilizer being brought inside the homes.