Los Angeles: Federal officials widened their probe into a possible terrorist motivation for Wednesday’s San Bernardino shooting rampage, sorting through computer records, tracking the travels of the shooting suspects and interviewing others the two spoke to in recent days.

A senior federal government official said agents believe suspect Syed Rizwan Farouq, 28, was in contact with a small number of people authorities suspect are extremists. The official said agents have picked up indications he “communicated” with at least one individual that US law enforcement officials were monitoring as a potential terrorism suspect.

The official, briefed on the matter but not authorised to speak publicly, said agents believe Farook’s connection to a potential terrorism suspect in this country might be someone he knew only tangentially.

But the source said the connection is enough to suggest there might be a “deeper terror matrix” behind the San Bernardino attacks, rather than simply workplace violence.

The official declined to provide more details about the potential terrorism suspect under surveillance in the US, except to add that the individual has not been charged in this country and that agents are still evaluating the relationship.

Representative Adam Schiff (Democrat-Burbank), the ranking minority member of the House Intelligence Committee, who has been briefed on the investigation, said Thursday that federal agents have yet to turn up evidence that Farouq was “radicalised.”

Phone records led authorities to three men who “were in phone contact” with Farouq and his wife, Tashfeen Malik, 27, according to a different source speaking confidentially because he was not authorised to speak publicly.

“They were associates and in contact with the shooters,” the official said.

The source did not know whether the men were cooperating, might be culpable in some way or whether they had provided any helpful leads in the investigation, which is now in FBI hands.

One of those identified, Roshan Zamir Abbassi, posted a message on his Facebook page saying that he had been interviewed by authorities but had nothing to do with the shooting.

“Held at gunpoint when LAPD, secret service, and FBI visited my house just a few hours ago,” Abbassi wrote. “My crime, the shooter used to come to our local masjid ... We Muslims condemn all acts of terror. ... We have nothing to hide and I repeat we condemn all acts of terror.”

A second man, Nizaam Ali, 23, told The Times the FBI came to his house in San Bernardino on Wednesday night and questioned him about his texts and phone calls to Farouq.

Ali said they had exchanged about 50 communications, usually about meeting at their mosque, but not since September when he sold Farouq a goat to sacrifice for the Eid Al Adha holiday.

When asked if Farouq was religious, Ali said, he only responded that he was “punctual in prayer.”

Meanwhile, the FBI and intelligence officials were tracking the suspects’ past travel patterns and searching their computer and telephone records for connections to known terrorists or people with extremist views inside and outside the US, a senior federal official said Thursday.

The official who spoke on condition of anonymity to discuss the ongoing investigation, said authorities have found evidence that Farouq, a US citizen, made at least two trips to Saudi Arabia, in 2014 and in 2013.

Law enforcement officials said Malik, who holds a Pakistani passport, entered the US on a K-1 “fiance visa” with Farouq in July 2014.

Given the amount of ammunition and number of homemade bombs found in the couple’s Redlands apartment, they appeared to have been planning for a complicated, large-scale attack, the official said. It’s still not clear why they decided to act on Wednesday.

US Atty Gen Loretta Lynch cautioned that the motive for the attack remains unknown.

“We don’t know if it was terrorism or workplace rage,” she said in a statement. “There is an investigation to determine why it happened, how did they obtain the means for this and what else might’ve been planned.”

At a news conference Thursday, David Bowdich, assistant director in charge of the FBI office in Los Angeles, said that whatever the motive was, the attack revealed significant advance preparation.

“The amount of armaments that he had, the weapons and ammunition, there was obviously a mission here,” Bowdich said. “We know that. We do not know why. We don’t know if this was the intended target, if there was something that triggered him to do this immediately. We just don’t know.”

Bowdich said Farouq returned to the US after some international travel in July 2014 and brought back Malik, who was not yet his wife. Bowdich said he didn’t know if the international travel had anything to do with the attack. The FBI is still researching which countries Farouq travelled to; he did go to Pakistan at one point, Bowdich said.

“It would irresponsible and premature of me to call this terrorism,” Bowdich said. “The FBI defines terrorism very specifically. That is the big question for us.”