SAN FRANCISCO — Seven men and a woman were indicted on charges related to a Sonoma County home invasion robbery spree that local authorities say is part of a disturbing trend centered on the pot industry.

Chrishawn Beal, Jaray Simmons, Ledarrell Crockett, Melvin Corbin, Nakia Jones, Siddiq Abdullah, Romello Jones, and Jade Johnson were indicted on charges of conspiracy, robbery, marijuana possession, and gun possession in furtherance of violence and drug trafficking. If convicted they face possible life sentences.

The eight were arrested after an attempted robbery spree in March, that involved an incident where one Petaluma homeowner was tied up and pistol-whipped. The suspects were all identified as North Carolina and Virginia residents, and police say they came to Northern California looking for marijuana grow houses to rob.

None of the intended targets turned out to be growing marijuana, police say. Three of the suspects were arrested at San Francisco International Airport, on their way to board a flight back to the East Coast.

Their arrests were one of at least three incidents since February where East Coast residents came to the Sonoma area looking to rob marijuana cultivators. On Feb. 8, five masked robbers entered two homes in Santa Rosa before dawn, restraining residents with duct tape in a quest for marijuana and money. One resident was shot and killed, and four suspects were arrested, the Press Democrat reported.

Earlier this week, a Miami man was arrested in Oakland in connection with a home invasion robbery in Sonoma County, where the residents were tied up and marijuana was stolen, authorities said.