SAN BERNARDINO, Calif. -- A U.S. official says the FBI was treating the mass shooting in California as a potential act of terror but had reached no conclusion it was.
The official was briefed on the investigation but wasn't authorized to discuss it by name and spoke on condition of anonymity.
The official said Syed Rizwan Farook communicated with individuals who were under FBI scrutiny in connection with a terrorism investigation. But the official said the contact was with "people who weren't significant players on our radar," dated back some time, and there was no immediate indication of any "surge" in communication ahead of the shooting.
The official said Farook and his wife weren't on the FBI's radar before the shooting, which killed 14.
The official said the communication was a "potential factor" but cautioned that "contact with individuals who are subjects of investigations in and of itself doesn't mean that you are a terrorist."
Farook was born in Chicago at the old Cook County hospital. He and his family moved away to California several years later.
The FBI says Tashfeen Malik came to the U.S. in July 2014 on a Pakistani passport and a so-called fiancée visa. To get the visa, she had to submit to an in-person interview and biometric and background checks to ensure she wasn't a threat to public safety or national security.
Police say they found 12 pipe bomb devices at a California home being searched in connection with a mass shooting as well as hundreds of tools that could be used to make improvised explosive devices.
San Bernardino Police Chief Jarrod Burguan said at a news conference Thursday that the attackers also left a device at the social service center where they opened fire. The device consisted of 3 connected pipe bombs with a remote control that apparently did not work.
Authorities say Farook and his wife killed 14 people at the center Wednesday. The chief says the attackers fired between 65 and 75 rounds at the center. They later died in a gunbattle with police.
Burguan also said the shooters had more than 3,000 rounds of ammunition at their home, 12 pipe bombs and hundreds of tools that could be used to make improvised explosive devices.
Burguan says Farook and his wife sprayed the room at a social service center in San Bernardino with bullets but police didn't know if any one person was targeted.
Police and the FBI say the attack was planned but they do not know a motive.
Burguan also says the number of people injured in the mass shooting has risen from 17 to 21.