WASHINGTON — The U.S. government appears not to have picked up on extremist messages exchanged during the online courtship two years ago between the American-born man accused in the California shootings and his future wife in Pakistan, according to lawmakers detailing closed-door briefings by federal officials on Capitol Hill.

American officials said 28-year-old Syed Rizwan Farook and his wife, 29-year-old Tashfeen Malik, discussed martyrdom and jihad online as early as 2013. But the couple never surfaced on law enforcement’s radar and Malik was able to enter the U.S. on a fiancie visa last year despite having professed radical views online.

Meanwhile, the investigation into the shootings that left 14 dead last week continued in San Bernardino, where an FBI dive team searched a small, urban lake about 3 miles north of the shooting site. A law enforcement official briefed on the investigation said divers are looking for a computer hard drive that may have been dumped in the lake. The official wasn’t authorized to speak by name about an ongoing investigation and spoke on condition of anonymity.

Authorities said the shooters, who killed 14 people at a holiday gathering on Dec. 2, had been in the area.

The couple died in a shootout with law enforcement hours after the attack and left behind a 6-month-old daughter.