Four men arrested on suspicion of pimping in Sonoma County during a national effort targeting child prostitution were from Sacramento, Oakland and Vallejo, authorities said.

Only one of the three teenage girls suspected to have been working in prostitution whom officers rescued during operations in Santa Rosa and Petaluma was a local resident, Sonoma County Sheriff's officials said.

The other two girls were from elsewhere in Northern California. They were ages 15 to 17.

The regional span of people involved in underage prostitution at local hotels illustrates the movement of pimps and child prostitutes throughout the Bay Area, said Sgt. Ruben Martinez, who runs the Sheriff's Office domestic violence/sex crimes team.

"There is a circuit," Martinez said.

"They move around, and they say where they'll go," Santa Rosa Police Sgt. Terry Anderson said.

Erotic advertisements on websites often include a range of locations where a prostitute might work.

Officers combed websites trying to identify girls who looked underage. Detectives don't just rely on appearance; they also look for other signs such as key words often used to hint to a potential customer seeking out juveniles, Anderson said.

"Child prostitution is not visible on the street anymore; they're using social networks," District Attorney Jill Ravitch said.

Over the past two years, law enforcement agencies have referred 18 human trafficking cases to the District Attorney's Office, Ravitch said.

Out of those cases, seven have resulted in convictions and six are still pending. Prosecutors filed charges in 35prostitution cases.

Sheriff's deputies and officers from the Santa Rosa, Petaluma and Rohnert Park police departments as well as an investigator and a prosecutor from the District Attorney's Office, coordinated stings in Santa Rosa on Thursday and in Petaluma on Friday.

Across the country, agencies participating in the FBI-run Operation Cross Country rescued 105 minors being exploited through prostitution and arrested 159 suspected pimps, according to the agency.

Preparation for the operations began weeks ago.

In Sonoma County, officers posed as customers at hotels, and a team of officers monitored and coordinated the events. The team involved about 20 people, including officers and deputies, as well as a Sonoma County District Attorney's Office prosecutor and investigator.

One of the men arrested appeared in court Tuesday.

Prosecutors charged Preston Eric Bouie Jr., 22, of Vallejo with child endangerment and aiding in prostitution during a hearing in department 9.

Bouie was holding his 3-month-old baby when he was arrested, said Chief Deputy District Attorney Bill Brockley, chairman of the Sonoma County Human Trafficking Task Force.

The case was continued to Aug. 14, when Bouie is expected to enter a plea. Bouie remained in Sonoma County Jail on Tuesday on $50,000 bail.

Two of the other men also were in custody at the Sonoma County Jail on Tuesday.

Quoc Pham, 26, of Sacramento was being held without bail on state parole and immigration holds as well as suspected aiding in prostitution, records show.

Noel Crosby, 31, of Oakland was being held on $10,000 bail on suspicion of pimping, aiding in prostitution and false imprisonment, jail records show.

William Kareem, 28, of Vallejo was arrested and cited on suspicion of a pimping-related charge, but he was not booked into the jail, Martinez said.

Additional details about his case weren't immediately available.

"The goal is to try to get these girls out of that lifestyle and take down the person that's behind it," Anderson said.

Staff from Verity, Crossing the Jordan Foundation and the Soroptimist Club of Sonoma County also participated in the two-day operation in Sonoma County. They provided services to the three juveniles contacted over the weekend.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.