The Pentagon is halting operational training for all Saudi military students studying in the United States while it investigates last week’s deadly shooting at Naval Air Station Pensacola by a Saudi airman, defense officials said.

The move is part of a “safety stand-down” ordered Tuesday by Deputy Secretary of Defense David Norquist under which the military will review how it screens foreign military students and grants them access to bases.

Flight training and other operational exercises will cease for the roughly 850 Saudi trainees in the U.S. pending the completion of the review, which could take a week or more, defense officials said. That means Saudi pilots, including several hundred studying at Naval Air Station Pensacola and other Florida bases, will be grounded for the time being.

Classroom training will continue after being suspended over the weekend.

The review is designed to strengthen vetting procedures for international military students so they align more closely with vetting procedures used for U.S. personnel, Norquist wrote in a memo Tuesday. It will cover roughly 5,000 international military students from more than 150 countries training in the country.

“As we affirm our commitment to these critical military partnerships, so must we assess the efficacy of our security procedures in light of the tragic loss of life on December 6, 2019, at Naval Air Station Pensacola,” Norquist wrote. “In doing so, we will make every effort to ensure the safety of all personnel and their families on U.S. military installations.”

Three young sailors were killed and eight people were wounded on Friday when a Saudi air force trainee opened fire in a classroom at the Pensacola base on Friday. The gunman, Ahmed Mohammed al-Shamrani, was fatally shot by a sheriff’s deputy responding to the attack.

The shooting immediately prompted questions from lawmakers about how the U.S. government scrutinizes candidates for military exchange programs.

The FBI was investigating the attack as an act of terrorism and are trying to learn whether the gunman was part of a larger network.