MARTINEZ -- Investigators are looking for renters who may have fallen victim to a scam involving foreclosed and otherwise unoccupied homes rented out without the legal owners' knowledge, Contra Costa County District Attorney Mark Peterson announced Monday.

The DA's office estimates that residents of more than 20 households have been paying rent to a Martinez man who prosecutors say illegally claimed ownership of homes in Brentwood, Antioch, Walnut Creek and Hercules and then advertised the properties as rentals on the website Craigslist.

Alfonso Salazar, a 62-year-old Martinez resident, was arraigned in Contra Costa Court on Monday afternoon on nine felony counts, including grand theft, second-degree burglary, perjury and filing false documents. It is unclear, at this early stage of the investigation, whether Salazar's Southern California employer, the National Alliance of Homeowners for Justice, had consent and knowledge of Salazar's criminal activities, deputy district attorney Ken McCormick said.

The National Alliance of Homeowners for Justice, which was listed as the lessor on these properties, did not return a call for comment Monday.

"We are expecting to flush out more victims as this investigation continues," said McCormick, who charged Salazar on Friday. The renters are at risk of being evicted by the true homeowners, which in most cases are banks.

Salazar, a former Countrywide Mortgage employee whose real-estate agent license expired last year, identified homes that were vacant, posted a note on the front door in which he claimed ownership in the name of the National Alliance of Homeowners for Justice unless anyone objected, and changed the locks, McCormick said. One house that Salazar rented out in Walnut Creek was owned by an Alameda County resident.

The values of the homes ranged from $215,000 to $742,000. A court order froze a bank account containing more than $35,000, but the total amount gained from the victims is so far undetermined.

The Walnut Creek, Brentwood and Hercules police departments caught wind of what was happening late last year, at which point district attorney senior inspector Darryl Holcombe took charge of the investigation, McCormick said. Salazar's alleged crimes date back to October.

McCormick said he has prosecuted people in the past for fraudulently renting out homes through Craigslist, but he has "never had anyone so organized and sophisticated and brazen about it."

Salazar returns to court March 6 to identify his public defender and enter a plea. He is being held in West County Jail in Richmond in lieu of $180,000 bail.

The District Attorney's Office asks anyone who has been paying rent to Salazar or the National Alliance of Homeowners for Justice to contact Holcombe at 925-957-8762.

Contact Malaika Fraley at 925-234-1684. Follow her Twitter.com/malaikafraley.