Four people were injured in the attack

Police in California have said a woman suspected of carrying out a shooting rampage at YouTube's headquarters in California is dead. 

Police say four people were injured in the gun attack in San Bruno, south of San Francisco. 

San Bruno Police Chief is Ed Barberini said officers are currently clearing the building:

“We have four victims who have all been transported for gunshot related injuries and we have one subject who is deceased inside the building with a self-inflicted wound who, at this time, we believe to be the shooter but we are still following up on that,” he said.

He refused to comment on reports that a second shooter - a man - was also at large.

Officers run toward YouTube headquarters in San Bruno, California, 03-04-2018. Image: Jeff Chiu/AP/Press Association Images

San Francisco General Hospital has confirmed that it received three victims from the incident.

Brent Andrew, a spokesperson for the hospital, said two women and one man had been admitted.

He said one of those is in a critical condition. Of the other two, one is in a serious condition and another is described as fair.

US President Donald Trump has thanked the "phenomenal law enforcement officers and first responders that are currently on the scene" saying his "thoughts and prayers are with everybody involved."

Earlier police confirmed they were “responding to an active shooter” at the YouTube campus.

Members of the public were urged the public to stay out of the area. 

YouTube product manager Vadim Lavrusik posted on Twitter: "Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers."

This Youtube staff member told CNN she was on a video call with a colleague inside the effected building when the incident began:

"We were all suddenly aware of a lot of noises and sounds of people running outside of the room where she was and people screaming," she said.

"The person who was in the room on the video conference in the building suddenly became very alarmed and was listening to the sounds and suddenly became very scared and said, 'I have to get out of here.'"

One witness told California TV station KTVU that she believed the shooter may have a “rapid-fire” weapon.

Images posted on social media showed people being lead with their hands up outside YouTube's office.

YouTube product manager Todd Sherman said he was in a meeting when he heard people running for the exit.

He said it “seemed serious and not like a drill.”  

In a string of tweets YouTube owner Google confirmed it was coordinating with local authorities in relation to the incident.

It said its security team has been working to help police “evacuate the buildings and ensure the safety of employees in the area.”

The company warned its employees to stay away from the area, adding “there is no need to take any action.”

A special helpline has been set up for employees.