At least 14 people were killed on Wednesday after a shooting at a social services centre in San Bernardino, California.

Hundreds of people were evacuated from the Inland Regional Center in San Bernardino. Seventeen victims were also injured in the attack, officials said.

Police said that after a stand-off involving police in their vehicles and a black SUV, they shot and killed two suspects. One of them was male and one was a woman. Officers said they were questioning a third person who was detained close to the scene of the stand-off but it was unclear whether he was involved in the incident.

"It quickly became clear we had an active shooter situation," San Bernadino Police Chief Jarrod Burguan said during a press conference on Wednesday afternoon.

“They came prepared as if they were on a mission."

Two women speak with a firefighter near the scene. Micah Escamilla/Los Angeles News Group/Associated Press (Doug Saunders/Los Angeles News Group/AP)

Agents with the FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives are currently pursuing the suspects, who were said to be wearing tactical gear and armed with "long guns." The shooting was reported at 11am local time.

Chief Burguan added that the attackers' motives were unclear.

"They came prepared to do what they did, as if they were on a mission," he said. "They came with a purpose."

A SWAT vehicle carries police officers near the scene in San Bernardino, California. Doug Saunders/Los Angeles News Group/Associated Press (Micah Escamilla/Los Angeles News Group/Associated)

Police had been searching for an SUV that fled away from the scene and have also detonated a suspicious device found at the building, the Los Angeles Times reported.

Terry Petit received a text from his daughter, Holly Pettit Graefe, as gunfire erupted inside her employers' building.

"People shot. In the office waiting for cops. Pray for us. I am locked in an office," he said, reading her text messages to the Associated Press.

The Inland Regional Center employs 670 staff members who provide services to more than 30,000 developmentally disabled people who live in San Bernardino and Riverside counties.

President Barack Obama told CBS News that he hoped the shooting could be contained.