The Contra Costa County District Attorney's Office last week announced felony and misdemeanor charges filed against an unlicensed contractor for allegedly defrauding multiple victims in the county.

Modesto resident Adan Contreras Rivas, 41, is being held on $600,000 bail in the Martinez Detention Facility on 38 charges, including those for financial elder abuse, theft by false pretense, theft with specified priors, and violations related to his fraudulent contracting practices.

Authorities have investigated Rivas since June, when initial accusations were reported by a Walnut Creek resident. Rivas was arrested in Morgan Hill on Nov. 8, when he was operating under the name "Gutierrez Tree Services".

He has also used other business names like "New View Tree Care". Prosecutors said in a statement that Rivas allegedly posed as a licensed contractor in the landscaping and paver industry and took thousands of dollars from unsuspecting consumers.

According to the DA's office, his alleged victims fit a particular profile: often elderly and residing in affluent neighborhoods in Walnut Creek and Concord. Investigators believe there are more victims around Contra Costa County, as well as the South Bay and the Central Valley.

Prosecutors said unlicensed contractors pose a threat to consumers by failing to acquire skills and licensure when hired to perform home improvement or construction projects. Some unlicensed contractors illegally require excessive down payments for construction or landscaping projects, and frequently fail to begin or complete projects once they receive money.

Consumers are often unaware unlicensed contractors don't have completed background checks and usually don't carry workers' compensation insurance for their employees -- which increases liability risks to consumers.

California law requires contractors to be licensed and possess workers' compensation insurance for employees. Licensed contractors are only allowed to request a down payment of $1,000 or 10 percent of the contract (whichever is less).

For more information on how to verify a contractor's license, people can go to cslb.ca.gov.