Divers have searched a California lake near the site of the San Bernardino massacre looking for evidence that may have been left by the husband and wife behind the attack.
The FBI said there were indications that US-born Syed Farook and his Pakistani wife Tashfeen Malik had visited the park where Seccombe Lake is located on the day of the 2 December shooting or previously.
Divers were looking for electronic devices, a hard drive and other items linked to the shooters.
“We would be remiss not to go into this lake and conduct a thorough search for any evidence items that may come back,” an FBI official said.
Authorities have said that the couple, who left behind a six-month-old daughter, had been radicalised for some time and practiced target shooting at a gun range days before the attack that killed 14 and injured 22.
Islamic militant groups ignored contact attempts from Malik in the months before she and her husband killed 14 people at a California holiday party, probably because they feared getting caught in a US law enforcement sting, US government sources said.
Disclosures of her overtures to extremists abroad surfaced as the investigation of the shooting rampage in San Bernardino, about 100km east of Los Angeles, appeared to take a new turn with divers searching a small lake near the scene of the massacre.
The number of organizations that Malik, 29, tried to contact and how she sought to reach them was unclear, but the groups almost certainly included al Qaeda’s Syria-based official affiliate, the Nusrah Front, the government sources said.
One source said investigators have little, if any, evidence that Malik or her husband Farook, 28, had any direct contact with Islamic State, which has seized control of large swaths of Syria and Iraq and claimed responsibility for assaults in Paris last month that left 130 people dead.
FBI Director James Comey has said Malik and Farook declared at about the time of their attack that they were acting on behalf of Islamic State, which in turn has embraced the couple as among its followers.
But US government sources have said there was no evidence that the Islamic State even knew of the couple before the killings.
Militant groups sought out by Malik likely ignored her approaches because they have become extremely wary of responding to outsiders they do not know or who have not been introduced to them, sources said.
The husband and wife were killed in a shoot-out with police hours after they opened fire with assault rifles at a holiday gathering of Farook’s co-workers at the Inland Regional Centersocial services agency in San Bernardino.