ALAMEDA COUNTY, Calif. -- Several organizations collaborated on Wednesday to conduct a sting operation for illegal prostitution in unincorporated Alameda County.

The Alameda County Sheriff's Office, the Dublin, Livermore, and Livermore police departments, the California Department of Corrections, the California Department of Justice, and the Alameda County Probation Department yielded 56 arrests at hotels in Castro Valley and Dublin.

Authorities used the Web site http://Craigslist.org to pose as customers inquiring about prostitutes willing to come to local hotels and perform sexual services for money or drugs, according to the Alameda County Sheriff's Office.

The operation in Dublin yielded 20 arrests for prostitution and seven arrests for aiding and facilitating someone to engage in the act of prostitution, according to the sheriff's office.

The Castro Valley operation yielded 15 arrests for prostitution, nine arrests for aiding or facilitating someone to engage in the act of prostitution, one arrest for sales of marijuana, one arrest for sales of methamphetamine, one arrest for the transportation and distribution of narcotics, one arrest for a parole violation, and one arrest for being under the influence of a controlled substance.