For the third day in a row, FBI divers searched Seccombe Lake in San Bernardino, California, Saturday for evidence on the slaughter of 14 people at the Inland Regional Center earlier in the month, local media reported. Agents were seen removing an item from the lake Friday but would not comment on whether it was linked with the attack.

“As I said on day one, we will leave no stone unturned,” said David Bowdich, assistant director of the FBI Los Angeles Field Office, the San Bernardino Sun reported. Bowdich told reporters the investigation into the Dec. 2 mass shooting would go on for some time and could expand to other areas and neighborhoods.

Syed Farook and his wife Tashfeen Malik committed the mass shooting at the Inland Regional Center during a holiday party and both later died in a shootout with police. Farook was a San Bernardino County employee. Investigators believe the couple stopped at the lake at some point after their crime, possibly disposing of evidence to cover their digital trail.

The object removed from the lake Friday was approximately the size of half a sandwich, the local newspaper reported. KNBC, Los Angeles, reported that two items were removed from the lake that might provide some link to how the couple planned the attack.

Investigators are searching for a digital trail, saying the couple had attempted to destroy evidence with two cell phones found in a dumpster near their home. A hard drive was missing from one computer they used, and NBC reported that one of the items recovered from the lake appeared to be the size of a hard drive.

Authorities have described Farook and Malik as “self-radicialized” and voicing support for the Islamic State group. Investigators told the Los Angeles Times Saturday one or both of the attackers probably were in direct contact with foreign terror groups. Recovering digital evidence would help investigators establish whether any direct links exist.

“At the worst, they were not only told to do something, but got help. We’re working toward the worst,” an official told the LA Times.