MARTINEZ, California — A 22-year-old Martinez mother has been arrested after police say she allegedly offered her four-year-old child for $500 to sexual predators surfing the internet in a Craigslist web personal ad.

Martinez police Shannon Nicole Woods was arrested on Tuesday after they received a tip from the National Center for Missing and Exploited Children regarding a posting on Craigslist that was soliciting for prostitution.

Authorities contacted Woods via the computer and learned that she had a four-year-old child and was also pregnant.

During these electronic conversations, an inquiry for sex and one regarding the child were made. Woods allegedly offered the child for sex for $500, according to police.

Authorities then served a search warrant at a residence in the 200 block of Thistle Circle and placed her into custody.

Woods was booked into the Contra Costa County Main Detention Facility and charged with offering a minor under 16 for lewd and lascivious acts. She is being held on a $50,000 warrant.