FBI spokeswoman Laura Eimiller confirmed to AFP that a search warrant was executed at a residence in Corona, an hour east of Los Angeles “to seek evidence in an ongoing investigation” but did not specify the case.
No arrests were made, she said.
The search warrant was executed on a sealed affidavit and authorities were barred from disclosing further details, Eimiller said.
Local media outlets identified the home as that of Farook’s brother.
Farook and his wife, Tashfeen Malik, opened fire on his coworkers in the California city of San Bernardinoon December 2, killing 14 people and wounding 22.
It was the deadliest terror attack in the United States since the September 11, 2001 attacks.
Farook and Malik were killed in a shootout with police.
The news comes with Apple and the US authorities in a standoff after the tech giant refused to comply with a judge’s order to help the FBI break into Farook’s iPhone.
Apple chief executive Tim Cook has said doing so would be an “unprecedented step which threatens the security of our customers” and would have “implications far beyond the legal case at hand.”
Prosecutors had requested Apple’s help after the FBI failed to crack the phone’s code two months into the investigation.