The California Highway Patrol (CHP) is facing a potential federal investigation after an officer was filmed repeatedly punching a black woman he had pinned down on the side of an Los Angeles freeway.

The footage went viral after a pasing Californian driver recorded the incident on his mobile phone camera and uploaded it onto YouTube. In the video, you can see the woman walk rapidly away from the officer, only to be thrown to the ground by the officer, who pins her down and punches her in the head several times. 

You can watch the video below (warning: contains graphic violence): 

David Diaz, who started filming when he saw the officer in pursuit of the woman, told CBS Los Angeles: "He just pounded her. If you look at the video, there are 15 hits. To the head, and not just simple jabs. These are blows to the head. Blows. Really serious blows. And this is ridiculous to me."

The video has since been watched nearly 300,000 times. In response to the growing storm of controversy, the California Highway Patrol released this statement: "We are aware of the video and we are looking into the incident. As a matter of policy, every time there is a use of force by our officers, there is a review conducted to determine whether the use of force was appropriate. That will be done in this case, however, since there is an ongoing investigation, it would be premature to comment on this specific video segment without reviewing the entire incident."

This isn't the first time that the CHP have faced accusations of police brutality. Last year, the state of California paid out $250,000 to a pregnant woman who had been kneed and hogtied by a Highway Patrol officer after being pulled over for talking on her mobile phone. In 2011, the same department nearly beat a truck driver to death after he asked to read a traffic ticket before signing it.