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FBI and police investigators are seen around a vehicle in which two suspects were shot following a mass shooting in San Bernardino, California, Dec. 3, 2015. Three associates of the alleged shooters are being sought for questioning. Reuters

Federal investigators Thursday sought three men who had been in touch with the suspected attackers in the mass shooting in San Bernardino, California, that killed 14 people and injured at least 21 others, the Los Angeles Times reported. A government official told the paper investigators wanted to interview the three men who “were in phone contact,” with suspected shooters Syed Farook and his wife Tashfeen Malik in the days leading up to the shooting rampage.

"They were associates and in contact with the shooters,” the official told the newspaper. The government official reportedly requested anonymity because the situation was delicate.

The identity of the men or if they had any involvement in the shooting was not yet clear. Farook, 28, and Malik, 27, were both killed in a gunfight with police following a chase after the mass shooting.

Federal officials said Thursday they had not ruled out terrorism as a motive. The shooting occurred Wednesday during "a Christmas gathering, holiday-type of luncheon," San Bernardino Police Chief Jarrod Burguan said during a press conference. Farook worked at the county health department and reportedly exited the party at a social services center angrily, then allegedly returned with his wife, armed with multiple weapons.

The suspects behind the shooting fired up to 75 rounds Wednesday and used an explosive device controlled by a remote control, Burguan said. "They sprayed the room with bullets, so I don't know if there was one person they openly targeted," he said.

The motive behind the shooting is still unknown. “It is possible that this was terrorist-related, but we don’t know,” U.S. President Barack Obama said Thursday in an address from the Oval Office. “It’s also possible that this was workplace-related."

Farook, a U.S. citizen who was born in Illinois had been described by family as a devout Muslim. His wife Malik was a Pakistani citizen in the country on a visa for fiancées. Farook's family denounced his actions, Newsday reported.

U.S. Defense Secretary Ash Carter said he felt authorities would "get to the bottom" of the situation during a press conference that was called to discuss his decision to open all combat positions to women.

“The protection of our people, including our service people, and concern about radicalization, including of American citizens living in America ... is an enormous concern," Carter said, offering his condolences to the victims' families. Authorities were expected to name all 14 victims Thursday.