Police in the city of South San Francisco say an officer was struck in the head with a skateboard and critically injured while chasing a suspect.

A police statement released early Friday said the officer was in surgery. The officer was pursuing the suspect Thursday afternoon after getting a report that someone was causing a disturbance.

Authorities say the man fled on a skateboard and then turned and used it to knock the officer unconscious. Another officer arrested the man.

The injured officer's name hasn't been released. Police didn't immediately return a telephone message seeking further information on the officer's condition.