Federal agents on Thursday morning served a search warrant at a Corona, California, home connected to the brother of Syed Farook, a shooter in the San Bernardino massacre.
FBI officials would not discuss the nature of the search, only saying federal agents were there seeking "evidence in an ongoing investigation." They collected a computer tower, envelopes and folders.
A Toyota SUV and a Lexus sedan belonging to Farook's brother and mother were also searched in the driveway.
Local news from across Southern California
No arrests were made, according to Laura Eimiller of the FBI.
"In this case there might have been a piece of evidence that came up in the investigation or a tip that said go back to this location, there's a critical piece of evidence that you need to look at," said Brian Levin, a professor in the Criminal Justice Department at Cal State University San Bernardino.
Neighbors said agents began knocking on doors between 5 and 6 a.m..
"They asked us a few questions about them, if we knew them and what was going on with them," said Brittani Adams, adding that the home had been visited by agents at least three times since the terrorist attack.
Neighbor Stacy Mozer said Farook's brother, Raheel, is a decorated U.S. military member who has a wife and young son.
"He's a very nice gentleman, very nice family, wonderful kid," Mozer said. "I just know that, hopefully that if they know something they can pass it on because there's no reason that they should have to suffer what someone else did in the family that was wrong."
Messages to the Farook family seeking comment were not returned.
A federal judge earlier this week ordered Apple to give investigators access to encrypted data on the iPhone used by Farook, but the tech giant is pushing back.
Apple CEO Tim Cook said Wednesday the company will resist the order. Cook asserted such a move would undermine encryption by creating a backdoor that could potentially be used on future devices.
The ruling comes after 10 failed password attempts caused the device to automatically erase all of the phone's contents, which the FBI said were critical. The iPhone found in the couple’s car belonged to Farook and was given to him by his former employer.
Fourteen people were killed and 22 others were wounded when Farook and his wife, Tashfeen Malik, opened fire at a holiday party at the Inland Regional Center in San Bernardino last December.
Nyree Arabian contributed to this report.