A Sacramento-area man faces charges of human trafficking following his arrest in a weekend prostitution sting in the Bay Area.  

Police in South San Francisco say undercover officers who'd pretended to be clients found a 17-year-old and an 18-year-old girl in a hotel room along with evidence of a prostitution operation.

They later arrested suspect Michael Pierce during a traffic stop.

Investigators say the 24-year-old Citrus Heights man used social media sites on the Internet to make friends with girls and entice them to work for him.  

Pierce remains in custody on charges including pimping and pandering.

Investigators say the younger girl turned out to be a runaway from Santa Clara County.