Federal authorities have charged 18 Bay Area residents in connection with a sophisticated marijuana growing operation spread among 50 homes in the Central Valley, the U.S. Attorney’s Office announced today.In a news conference in Sacramento this afternoon, U.S. Attorney Lawrence Brown, along with other law enforcement agencies, announced that a federal grand jury returned three new indictments charging 14 men and women with conspiracy to cultivate large quantities of marijuana.One of these individuals, along with four other Bay Area residents, faces a combined 26 counts of mail fraud in a separate indictment. Federal agents said that the five committed mortgage fraud in order to purchase 26 of the homes used to grow marijuana.While the indicted men and women are all Bay Area residents, Brown said they based their operation in the Central Valley because of the lower housing costs and relative anonymity of large suburban housing developments. According to U.S. Drug Enforcement Administration estimates, the ring produced nearly 11 tons of marijuana annually, with a street value of $96 million.Of those charged in the marijuana conspiracy, 11 are San Francisco residents: Dickson Hung, 35, Jiang Liang, 28, En Lin, 23, Rui Liu, 22, Lup Li, 39, Joyce Wang, 32, Zhi Lin, 50, Can Zhen, 32 and Siming Zhu, 32. The other four facing marijuana charges are: Kong Li, 46, of Castro Valley; Khin, or Kenny, Ung, 49, of San Leandro; Lian Li of Alameda; and Guo, or Ivan, Lu, 29, of Milpitas.Hung was also charged in the mortgage fraud scheme. Karen Lee, 29, of San Francisco, Wayne Feng, 29 of Oakland, and Wing Chang, 27, of San Francisco were also charged.The DEA, Internal Revenue Service, police from Lathrop, Stockton and Elk Grove, along with the San Joaquin County Sheriff’s Office, all cooperated on the investigation.Prosecutors said the defendants ran commercial marijuana gardens out of about 50 homes in Sacramento, Elk Grove, Stockton, Lathrop, Tracy and Modesto in 2006 and 2007.Authorities recovered about 24,500 marijuana plants during initial raids on the homes.The effort, dubbed Operation Marvin Gardens, was”a crackdown on one of the largest,most sophisticated residential indoor marijuana growing organizations in the nation,” according to DEA Assistant Special Agent in Charge Gordon Taylor.”Nobody was living in these homes,” he said. “They were gutted and retrofitted for the purpose of cultivating marijuana.”According to Taylor, the defendants sought out relatively new four-bedroom houses in suburban “cookie cutter communities.” The homes’ interior walls and ceilings were gutted, he said, and the group ran 18-inch ventilation ducts throughout the house to dissipate the odor.Sophisticated lighting systems and indoor irrigation systems were all run on timers. The equipment for all 50 homes cost an estimated $1.5 million, Taylor said.Today’s indictments are the latest product of an investigation that began in 2006. The original indictments from 2006 and 2007 charged 17 others with conspiracy to manufacture marijuana. All but two of those defendants have pleaded guilty, and the others remain at large.The earlier arrests were “primarily the workers on the grow site,” Taylor said. With this latest round of arrests, he said the investigation has “moved up the chain.” He said everyone arrested thus far has ties with the Bay Area.While Taylor could not comment on how big a role the 18 defendants played within the organization, he said the investigation is “definitely continuing.”If convicted, those facing cultivation charges face at least 10 years in prison, with a possible maximum life sentence. Those facing mail fraud charges would face a maximum possible sentence of 20 years in prison.