Training for more than 800 Saudi Arabian military students in the United States could resume, the Pentagon said Thursday, weeks after a Saudi gunman killed three U.S. sailors at a Florida base.

The military halted flight and field training for around 850 Saudi students amid fears that some knew about or were involved in the deadly attack at the Pensacola Naval Air Station.

“We're looking forward to turning it back on in the coming days,” Jonathan Hoffman, chief spokesman for the Defense Department, said during a press briefing.

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He said an announcement will probably come soon.

Security screenings of the students have been completed, and 21 were being expelled from the U.S. The trainees who were removed had jihadist or anti-American sentiments on social media pages or had “contact with child pornography,” including in Internet chat rooms, officials said.

None are accused of having knowledge of the shooting allegedly carried out by 21-year-old Saudi Air Force officer Mohammed Alshamrani. Attorney General William Barr said Alshamrani was "motivated by jihadist ideology" when he killed three sailors and wounded eight people in the Dec. 6 attack.

"During the course of the investigation, we learned that the shooter posted a message on September 11, [2019] stating, ‘the countdown has begun,’" Barr said Monday. "During the Thanksgiving weekend, he then visited the 9/11 Memorial in New York City.

The NAS Pensacola shooter was identified as Mohammed Alshamrani, a 21-year-old 2nd lieutenant in the Royal Saudi Air Force who was a student naval flight officer of Naval Aviation Schools Command. (FBI)

The NAS Pensacola shooter was identified as Mohammed Alshamrani, a 21-year-old 2nd lieutenant in the Royal Saudi Air Force who was a student naval flight officer of Naval Aviation Schools Command. (FBI)

"He also posted other anti-American, anti-Israeli and jihadi messages on social media, including two hours before his attack," he added.

He described the attack as an "act of terrorism."

The shooting raised concerns over the presence of foreign students on American military installations and exposed the shortcomings of cadet-screening procedures. Saudi Arabia is a key U.S. ally in the Middle East.

Saudis have received training at the Pensacola site since the 1970s, with as many as 20 students in any given class. Barr praised the program, describing the Royal Saudi Air Force as an "important military partner" that "has long had a training relationship with the United States."

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The shooting prompted some Navy instructors to ask the military for permission to arm themselves. Meanwhile, Barr asked Apple to unlock two iPhones that belonged to the suspected shooter to help extract data.

The company previously resisted efforts by law enforcement to access customers' private information but told Fox News it was cooperating in the Pensacola investigation.

Fox News' Greg Norman and The Associated Press contributed to this report.