The U.S. Marshals Service and Lakewood police are asking for the public's help to find a man who's a convicted sex offender — and a 16-year-old girl who may be with him.

Deputy U.S. Marshal Robert Rodriguez said Matthew Preston Caulk, 40, is wanted in Yellowstone County, Mont., for failing to register as a sex offender.

He was convicted of sexual misconduct with a child in Pierce County, Wash., in 2002.

Caulk was last seen on Sept. 26 in both Morrison, Colo., and Lakewood, Colo., authorities said. Amber Nicole Westbrook was seen with Caulk in Morrison, Rodriguez said.

Caulk is white, 5-foot-7, 140 pounds, with hazel eyes and shaved brown hair. He also has multiple tattoos.

Westbrook is white, 5-foot-7, 160 pounds, with blond hair, blue eyes and pierced ears.