Authorities are investigating whether the couple suspected of killing 14 people at a Christmas party in California had links to Islamist militants, as images were released of weapons and ammunition seized after they engaged in a shootout with police.

Syed Rizwan Farook, 28, and his wife, Tashfeen Malik, 27, were killed in the shootout five hours after the massacre at the Inland Regional Centre social services agency in the city of San Bernardino in California.

Twenty-one people were wounded in the attack, which ranks as the deadliest instance of US gun violence since the December 2012 shooting at Sandy Hook Elementary School in Newtown, Connecticut, in which 27 people were killed.

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Syed Rizwan Farook and his wife, both now dead, are the chief suspects. Photo: DMV

The dead and wounded accounted for nearly half of the estimated 75 to 80 people who were in the room where the armed couple opened fire.

San Bernardino Police Chief Jarrod Burguan said a search of a townhouse, leased by the two shooting suspects in the nearby community of Redlands, turned up thousands of rounds of ammunition, a dozen pipe bombs, flash drives, computers and mobile phones.

Officials in Washington, familiar with the investigation, said there was no hard evidence of a direct connection between the couple and any militant group abroad, but the electronics would be checked to see if the suspects had been browsing on jihadist websites or social media.

One US government source said the FBI was examining information indicating that Farook was in contact with individuals who had themselves been under FBI investigation, some from cases already closed.

The source also said it was possible that one or more of the contacts under scrutiny were overseas.

But no information has emerged suggesting any ties or contacts between Farook and the Islamic State (IS) group or other specific militant groups, the source said.

Obama says ‘it could be terrorist or workplace-related’

This is the bullet-ridden car driven by the couple to their deaths. Photo: San Bernardino Sheriff’s Dept

Officials, from president Barack Obama to Police Chief Burguan, said the attack may have been motivated by extremist ideology, but questions of motive remained unanswered.

“It is possible that this was terrorist-related. But we don’t know,” Mr Obama said.

“It is also possible that this was workplace-related.”

Farook, a US citizen born in Illinois, was the son of Pakistani immigrants, according to Hussam Ayloush, who heads the Los Angeles area chapter of the Muslim advocacy group Council on American-Islamic Relations (CAIR).

Malik, who had a six-month-old daughter with Farook, was a Pakistani native living in Saudi Arabia when they married, Mr Ayloush said.

FBI assistant director David Bowdich said Malik was admitted to the US on a K-1 (fiancee) visa and was travelling on a Pakistani passport.

The couple entered the US in July 2014 after a trip that included Pakistan, Mr Bowdich said.

Farook also visited Saudi Arabia for nine days in the summer of 2014, the kingdom’s embassy in Washington said.

The director of the Islamic Centre of Riverside, a mosque Farook attended regularly for two years, described him as a devout Muslim who made the pilgrimage to Mecca in Saudi Arabia a few years ago and celebrated his wedding reception at the mosque.

“His degree of faith is very high,” the director, Mustafa Kuko, said.

“He was a very quiet person, peaceful, never had an argument with anyone, or a dispute.”

Large amounts of ammunition were found inside the vehicle. Photo: San Bernardino Sheriff’s Dept

Mr Kuko said Farook attended morning and evening prayers from 2012 to 2014, when he abruptly stopped coming.

Farook, who according to Cheif Burguan had no criminal record, worked as an inspector for San Bernardino County environmental health department, the agency throwing the party that came under attack.

Police cited witness accounts that Farook had been attending the celebration but stormed off in anger, then returned with Malik armed with assault gear and opened fire.

Chief Burguan said they sprayed the room with 65 to 70 rounds.

Police officer Mike Madden, one of the first to arrive on the scene, recalled the pandemonium and sheer panic he encountered entering the hall, reeking with the smell of gunpowder and doused in blood and spray from the automatic sprinkler system as fire alarms wailed.

“It was unspeakable, the carnage we were seeing,” he recounted at an evening news conference in San Bernardino.

More weapons, 1,600 rounds of ammunition found in vehicle

Chief Burguan said the couple had two assault-style rifles, two semi-automatic handguns and 1,600 rounds of ammunition in their rented sport utility vehicle when they were killed.

At the townhouse, police found another 4,500 rounds, 12 pipe bombs and bomb-making equipment. One bomb was rigged to a remote-control device.

The guns were legally purchased in the US said Meredith Davis, a spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The couple were dressed in tactical gear. Photo: San Bernardino Sheriff’s Dept

Chief Burguan said Farook bought the two handguns. The rifles were purchased by someone else, who Ms Davis said was not linked to the investigation.

As the FBI-led investigation pressed on, authorities completed formally notifying the families of the 14 people who died and made their names public.

The victims, all from Southern California, ranged in age from 26 to 60, and most were men, according to the county coroner.

All but two of the dead and three of the wounded were county employees.

In addition to sparking further debate on gun control laws, the latest slaying in the country took place with much of the world on edge following the November 13 attacks in Paris by Islamic State militants that killed 130 people.

Mr Ayloush urged the public not to jump to conclusions about the motives behind the San Bernardino attack.

He said he was concerned about a backlash against the Muslim community in view of the rise of IS and some opposition among politicians and the public in the US over its plans to accept Syrian war refugees.

“We’re living in a very difficult time,” he told CNN.

“There’s a lot of Islamophobia out there, a lot of anti-Muslim sentiment, fuelled by pundits here and there, trying to blame a whole community for the acts of a few.”

About 200 worshipers gathered on Thursday night at the Ahmadiyya Muslim Community mosque, San Bernardino’s largest, to hold a vigil for victims of the shooting.

Meanwhile, a larger, more diverse crowd, estimated by police at about 3,500, packed the San Manuel Stadium, a municipal baseball park downtown, for a candlelight memorial.

“We’re here to support our community and be a visual representation of the actual religion of Islam, to show we are caring,” said Samar Natour, 16, wearing a pale blue hijab head scarf and holding a sign with a hand-drawn American flag and the message: “We stand with San Bernardino.”

Fighting back tears, Anthony Quayle, 33, said he was emotional seeing the community draw together in the face of tragedy.

“I’ve grown up in this city. I love this city, and I want to be a part of bringing it back together.”

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