FRESNO, Calif. (KFSN) -- A Fresno police officer has been caught up in a prostitution investigation -- with connections to the world famous bunny ranch. The officer resigned from the department last week.Officer Robert Knight has not been arrested or charged with any crime, but the hooker he identified as his girlfriend has. Police got her for prostitution after going through the officer to arrange for sex.At the historic Moonlite Bunny Ranch, prostitution is legal, and these photos of bunny "Allie Marie" are the tamest we could find. The photos on her Twitter page are sometimes even racier and one in particular caught the eyes of Fresno police. The same photo popped up on a Craigslist posting apparently offering up sex in the Fresno area, and the bathroom belonged to a Fresno police officer.Action News discovered a search warrant detailing how officer Robert Knight and the woman, whose real name is Alicia Stapleton, seemed to work together. Investigators say Knight answered her Craigslist ads and communicated with potential clients via Twitter, where he also tried talking to Hugh Hefner.Knight scheduled Stapleton's July 9 meeting with a potential client who was really an undercover officer. Police arrested her about 30 minutes into the meeting. ABC30 legal analyst Tony Capozzi says investigators will use the search warrant to bolster the case against Knight."What they want to do now is look at his telephone records, his email records, his Twitter records to see if there are other conversations similar to this," Capozzi said.The warrant reveals Knight was especially interested in fixing up Stapleton with Saudis who were supposed friends of the undercover officer. Capozzi says the interaction could reveal a bigger crime, like federal sex trafficking."It's not just this one person and this one incident," he said. "He's looking to expand this enterprise."Stapleton is now facing a misdemeanor solicitation charge. Police tell us they'll meet with prosecutors next week to determine if Knight should also face charges for supervising or aiding a prostitute. We tried to reach him for comment, but couldn't get in contact.