The Navy has grounded more than 300 Saudi military exchange students from flight training, the service said Tuesday.

The move comes after a Saudi student pilot killed three U.S. sailors at Naval Air Station Pensacola, the Florida base where he was undergoing training.

“They are currently doing a safety stand-down, an operational pause, in their flight training,” said Navy spokesperson Lt. Andriana Genualdi.

While the pause in flight operations is of unknown duration, the classroom portion of their training “will resume this week,” she said.

Of the more than 300 grounded Saudi students, 140 are at Pensacola, 128 are at Naval Air Station Mayport and 35 are at Naval Air Station Whiting Field, all in Florida, according to Genualdi.

Law enforcement officials have questioned other Saudi students at Pensacola, some of whom reportedly took cell phone video at the scene of the attack.

In addition to the three sailors killed, another eight persons were wounded in the shooting. The attacker, a Royal Saudi Air Force second lieutenant, was killed at the scene, and investigators are trying to determine his motive.

On Monday, the U.S. Northern Command ordered military bases around the country to implement new security procedures, including more random checks, in the wake of the Pensacola attack and another shooting earlier in Hawaii.