SAN BERNARDINO, Calif. -- The FBI announced Friday that it is investigating the mass shooting at a California office party as an act of terrorism, but the agency's director said there is no indication that the husband and wife who killed 14 were part of a larger plot or members of a terror cell.

Authorities did not cite specific evidence that led them to the terrorism focus, but a U.S. law enforcement official said the wife, Tashfeen Malik, under a Facebook alias had pledged allegiance to the Islamic State group and its leader. A Facebook official said Malik praised the group in a post at 11 a.m. Wednesday, when the couple were believed to have stormed a social service centre and opened fire.

Malik and her husband, Syed Farook, died several hours later in a gunbattle with police.

The IS-affiliated news service Aamaq called Malik and Farook "supporters" of their cause but stopped short of claiming responsibility for the attack.

FBI Director James Comey would not discuss whether anyone affiliated with the Islamic State communicated back to Malik, but he said there was no indication yet that the plot was directed by ISIS or any other foreign terror group.

"The investigation so far has developed indications of radicalization by the killers and of potential inspiration by foreign terrorist organizations," Comey said.

Despite mounting signs of the couple's radicalization, there "is a lot of evidence that doesn't quite make sense," Comey added.

The U.S. official who revealed the Facebook post was not authorized to discuss the case publicly and spoke on condition of anonymity.

The Facebook official, who also spoke on condition of anonymity because the person was not allowed under corporate policy to be quoted by name, said the company discovered Wednesday's post on Thursday, removed the profile from public view and reported its contents to law enforcement.

Attorneys representing Farook's family said Friday that none of his family members had any indication either he or his wife held extremist views.

Attorneys for Farook's family urged the public not to rush to judgment.

"If the most evidence there is to any affiliation is a Facebook account under another person's name ... then that's hardly anything at all," attorney David Chesley said.

Farook and Malik rented a townhome where investigators said they found an arsenal of ammunition and homemade bombs. On Friday morning, the property's owner allowed reporters inside. An upstairs bedroom had a crib, boxes of diapers and a computer. The couple had a 6-month-old daughter.

The FBI said analysts were trying to retrieve data from two cellphones found near there that had been crushed in an apparent attempt to destroy the information inside.

Farook had no criminal record, and neither he nor his wife was under scrutiny by local or federal law enforcement before the attack, authorities said.

Malik, 27, was a Pakistani who grew up in Saudi Arabia and came to the U.S. in 2014 on a fiancee visa. Farook, a 28-year-old restaurant health inspector, was born in Chicago to Pakistani parents and raised in California.

Law enforcement officials have long warned that Americans acting in sympathy with Islamic extremists -- though not on direct orders -- could launch an attack inside the U.S. Using slick propaganda, the Islamic State in particular has urged sympathizers worldwide to commit violence in their countries.

Two weeks ago, with Americans on edge over the Islamic State attacks in Paris that left 130 people dead, Comey said U.S. authorities had no specific or credible intelligence pointing to an attack on American soil.

Since March 2014, 71 people have been charged in the U.S. in connection with supporting ISIS, including 56 this year, according to a recent report from the George Washington University Program on Extremism. Though most are men, "women are taking an increasingly prominent role in the jihadist world," the report said.

It was not immediately clear whether Malik exhibited any support for radical Islamists before she arrived in the U.S.

Friends of the soft-spoken Farook who knew him from his daily prayers at a mosque in San Bernardino said they saw nothing to make them think he was violent. They said Farook reported meeting his future wife online.

To receive her visa, Malik was subjected to a vetting process the U.S. government describes as vigorous. It includes in-person interviews, fingerprints, checks against terrorist watch lists and reviews of her family members, travel history and places where she lived and worked.

Foreigners applying from countries that are home to Islamic extremists, such as Pakistan, undergo additional scrutiny before the State Department and Homeland Security approve their applications.

Pakistani intelligence officials said Malik moved as a child with her family to Saudi Arabia 25 years ago.

A person close to the Saudi government said Tashfeed Malik did not stay in Saudi Arabia, eventually returning to Pakistan and living in the capital Islamabad, though she returned to Saudi Arabia for visits. The person was not authorized to speak publicly, and did so on condition of anonymity.

Abdollah reported from Washington. Contributing to this report were Associated Press writers Ken Dilanian and Eric Tucker in Washington; Zarar Khan in Islamabad, Pakistan; Brian Skoloff in Redlands, California; Kimberly Pierceall in San Bernardino, California; Lee Keath in Cairo, Egypt; Mike Blood, Gillian Flaccus, Christine Armario, Sue Manning and Justin Pritchard in Los Angeles.