California shooter may be linked to IS

A woman accused of joining her husband in killing 14 people in California apparently pledged allegiance to a leader of the militant group Islamic State, two US government sources said on Friday, as intelligence officials in her native Pakistan pressed the investigation overseas.

Tashfeen Malik, 27, and her husband, Syed Rizwan Farook, 28, were killed in a shootout with police hours after the Wednesday massacre during a holiday party at the Inland Regional Center social services agency in San Bernardino, about 100 km east of Los Angeles. The attack was the deadliest mass shooting the US has experienced in three years.

US investigators are evaluating evidence that Malik, a Pakistani native who had been living in Saudi Arabia when she married Farook, had pledged allegiance to Islamic State leader Abu Bakr al-Baghdadi, two US officials told Reuters. They said the finding, if confirmed, could be a "game changer" in the investigation.

The couple had two assault-style rifles, two semi-automatic handguns 6,100 rounds of ammunition and 12 pipe bombs in their home or with them when they were killed, officials said. A U.S. government source said because of the amount of weaponry, investigators are trying to determine if they intended to carry out a more elaborate attack.

Farook, a U.S. citizen born in Illinois and the son of Pakistani immigrants, worked as an inspector for the San Bernardino County Department of Environment Health, the agency whose holiday party he and Malik allegedly attacked on Wednesday.

Investigators are looking into a report that Farook had an argument with a co-worker who denounced the "inherent dangers of Islam" prior to the shooting, a U.S. government source said.

While the attack may have been inspired by Islamic State, there is no evidence that it was directed by the militant group, U.S. government sources said. Islamic State, which has taken control of large parts of Syria and Iraq, took claim for the Nov. 13 attacks in Paris in which gunmen and suicide bombers killed 130.

CNN reported on Friday that one U.S. official said Malik had made the pledge to al-Baghdadi in a posting on Facebook on Wednesday, the day of the attack, under an account that used a different name.