Four FBI dive teams have started searching Secombe Lake at a park in San Bernardino, Calif., near where the mass shooting that left 14 dead occurred nine days ago, as the investigation into the incident continues.

FBI Assistant Director in charge David Bowdich said the search was prompted by a tip the FBI received, which alleged that Syed Rizwan Farook and Tashfeen Malik, who carried out the attack, were seen at the park on the day of the attack, according to ABC News. He declined to reveal what the dive teams were searching for, only saying that they was seeking "anything that had to do" with the shooting.

"In the end we may come up with nothing," he said, according to the Associated Press, adding that the investigation is massive and is going to take some time. "We just don't know yet."

Bowdich later added that there is "no belief there is anything dangerous" in the park.

Despite his refusal to reveal what's going on, there is at least one rumor about what the dive teams are looking for. An unidentified source has reportedly told CBS News that the FBI is searching for a hard drive that was missing from the suspects' home.

During the announcement, Bowdich also revealed that 22 people, not 21, were injured during the shooting. One victim apparently didn't realize at first that she was hurt, and later checked herself into the hospital. He also addressed a 2012 terror plot in Riverside, Calif., when four suspects were arrested and convicted of terrorism, noting the plot was to join the Taliban and fight overseas.

"There was never a danger to this community," he said.