The San Mateo County Sheriff's Office is looking for information about a strong-arm robbery Thursday night in which a woman leaving an apartment complex was struck in the head before having her valuables stolen.

The woman was leaving the complex at 57 Berkshire Ave. in unincorporated Redwood City at about 7:40 p.m. Thursday. She was on the ground floor near a stairwell when an unknown suspect suddenly struck her from behind with a piece of PVC tubing, authorities said.

The suspect then yanked a plastic grocery bag containing numerous pieces of jewelry from the stunned woman.

The suspect is described as a Hispanic man who is approximately 5 feet 7 inches tall and was wearing dark pants and a dark-colored crew neck sweater at the time of the attack, according to the sheriff's office.

Anyone with information about the attack is asked to contact sheriff's detectives at (650) 599-1536 or Sgt. Linda Gibbons at (650) 363-4063.

Anonymous callers can leave information at the tip line at (800) 547-2700.