California shooting: What you need to know

Wounded are transported from the scene of a shooting in San Bernadino, California.

Twelve people are dead at least 20 injured after a mass shooting at a disability centre in San Bernadino, California.

Here's what we know so far:

The victims

At least 12 people killed and up to 20 injured.

The San Bernardino Fire Department tweeted that it was responding to a "20 victim shooting incident". It's still a "very active scene" and the number of victims is expected to rise.

The gunmen

There may be up to three heavily armed gunmen, reports say. The fire department said the shooters were possibly wearing body armour. They were seen in military clothing and wearing black ski masks.

A witness told CNN the suspects fled in a black SUV.

The scene

The Inland Regional Centre provides social services to people with developmental disabilities.

It employs nearly 670 staff at its facilities in San Bernardino and Riverside counties, helping more than 30,200 people. It is unclear how many people were at the facility at the time of the shooting.

The shooting was centred around a building that houses at least 25 employees as well as a library and conference center.

Reports of possible bomb

Officers at the scene were heard referring to suspicious device as an "IED" - improvised explosive device. First responders were told to keep their distance from the south building.

A man told CNN police were checking the scene for the possibility of a bomb.