Bomb equipment, weapons and thousands of rounds of ammunition were found at the home of the San Bernardino shooters, US police have said, the BBC reports.
Police found the weaponry following the shootout of the two suspects after they killed 14 people and wounded 21 more at a social services centre.
Authorities still have not found a motive in the attack by Syed Rizwan Farook, 28, and Tashfeen Malik, 27.
Police said the attack indicated there had been “some degree of planning”.
San Bernardino Police Chief Jarrod Burguan said it appeared that the duo was prepared to carry out another attack.