The FBI on Friday formally confirmed that it is investigating the mass shooting in San Bernardino, Calif., as an act of terrorism.
"As of today, based on the information and the facts as we know them, we are now investigating these horrific acts as an act of terrorism," David Bowdich, assistant director of the FBI's field office in Los Angeles, said during a news conference.
Investigators had previously said they recovered 12 pipe bomb-type devices, tools for making improvised explosive devices and thousands of rounds of ammunition in the suspects' home.
Bowdich said Friday that there are "a number of pieces of evidence that [have] essentially pushed us off the cliff to say we are now investigating this as an act of terrorism."
Earlier in the day, multiple news outlets reported that Tashfeen Malik, one of the two suspects, had posted a declaration of allegiance to the Islamic State in Iraq and Syria (ISIS) on Facebook.
"We don't know all the answers to that yet," Bowdich said Friday, emphasizing that investigators were combing through potential evidence linked to the terrorism investigation.
The two suspects in the case, Malik and husband Syed Farook, died during a shootout with police Wednesday after the shooting at a San Bernardino social center that left 14 dead and 21 injured.
The FBI said Friday the suspects "attempted to destroy their digital fingerprints," saying investigators had found two crushed cellphones in a nearby trashcan.
Bowdich indicated that investigators were working to retrieve information from the devices.
He said authorities had confirmed that at least one of the suspects communicated by phone with someone federal authorities have monitored for potential terror ties.
Updated at 3:54 p.m.