At least 20 people have been injured in a mass shooting at a medical and health centre in San Bernardino, California.

The local San Bernardino Police Department has put the area on “lockdown” and is working to clear the scene in the vicinity of Orange Show Road and Waterman Ave near the Park Center.

A local reporter Tweeted that authorities were evacuating the Inland Regional Center, a non-profit medical and health organisation.

The incident remains an active shooter situation, and the San Bernadino County Sheriff has warned the public to stay clear of the area.

Videos posted to social media show people lying on the floor, and police aiding the wounded.

Multiple agencies, including the FBI and ATF, are currently attending the scene.