WASHINGTON –

U.S. investigators are increasingly convinced the California shooters planned multiple attacks, given their stockpile of weapons, and are looking at whether the Pakistani woman involved radicalized her American husband, officials said on Sunday.

Investigators believe the weapons cache collected by Tashfeen Malik, 29, and her husband, Syed Rizwan Farook, 28, points to more attacks but they do not have evidence on other possible targets, a senior U.S. government source told Reuters.

The couple stormed a gathering of civil servants in San Bernardino, California, on Wednesday, opening fire with assault-style rifles and killing 14 people. The pair were killed a few hours later in a shootout with police.

U.S. authorities were trying to learn what contacts Malik might have had with Islamic militants Pakistan and Saudi Arabia, where she grew up, the official said on condition of anonymity.

They lack clear evidence that the wife was radicalized overseas or that she in turn radicalized her husband, though they are actively investigating that, the official said.

Malik's estranged relatives in Pakistan have said she appeared to have abandoned the family's moderate Islam and become more radicalized in Saudi Arabia, where she moved as a toddler.

She returned to Pakistan and studied pharmacy at Bahauddin Zakaria university in Multan from 2007 to 2012.

"There's a serious investigation ongoing into what she was doing in Pakistan and in Saudi," U.S. Rep. Michael McCaul said on "Fox News Sunday." "We think that she had a lot to do with the radicalization process and perhaps with Mr. Farook's radicalization from within the United States."

"The wild card here is the wife Malik," said McCaul, the Republican chairman of the House Homeland Security Committee. He said investigators were also looking at where they got the money to acquire the guns.