More than a dozen Saudi servicemen training at various American military facilities will be expelled from the US after officials conducted an investigation in the wake of the December Naval Air Station Pensacola shooting.

On December 6 gunman Mohammed Saeed Alshamrani, an aviation student from Saudi Arabia, opened fire at the Florida base and killed three Americans - Airman Apprentice Cameron Scott Walters, 21; Mohammed Haitham, 19; Joshua Kaleb Watson, 23; and injured eight others.

He was participating in a training program sponsored by the Pentagon in a security cooperation agreement with Saudi Arabia that teaches English, basic aviation and initial pilot training.

More than 850 Saudi nationals are in the US participating in that program, a Department of Defense official stated.

More than a dozen Saudi servicemen training at US military bases across the nation will be expelled from the US following an official investigation into December's deadly shooting at Naval Air Station Pensacola in Florida (above)

On December 6 gunman Mohammed Saeed Alshamrani, an aviation student from Saudi Arabia, opened fire at the base and killed three Americans (L to R): Airman Apprentice Cameron Scott Walters, 21; Mohammed Haitham, 19; Joshua Kaleb Watson, 23; and injured eight others

Following the attack, the FBI and the Pentagon began a review into a slew of Saudi trainees studying at US military installations across the nation and now more than a dozen will be expelled after some were found to be linked to extremist movements, CNN reported Saturday evening.

Additionally, some were found to be in possession of child pornography.

However, none of these trainees being expelled are accused of being co-conspirators with shooter Alshamrani.

After the December 6 attack about a dozen Saudi trainees were confined to their quarters in Pensacola while the FBI investigated the shooting as a possible terror attack.

'In the wake of the Pensacola tragedy, the Department of Defense restricted to classroom training programs foreign military students from Saudi Arabia while we conducted a review and enhancement of our foreign student vetting procedures. That training pause is still in place while we implement new screening and security measures,' the Pentagon said to Fox News in a statement.

The Justice Department is also expected to conclude that the Pensacola attack was an act of terrorism, CNN reported. Investigators believe Alshamrani acted alone.

However, none of these trainees being expelled are accused of being co-conspirators with shooter Alshamrani (above)

It comes after the top lawyer for the FBI sent a letter to Apple on Monday, requesting the tech company's help to get past the passwords on the 21-year-old shooter's iPhones. The shooter had two iPhones with him when he attacked the base.

One of them he took with him and the other he left in the car. The phone he took with him in the attack he shot, leading cops to believe there may be key information on it.

Information on his Twitter account led investigators to believe he was radicalized.

Apple said it is cooperating with the FBI in its investigation.

'We have the greatest respect for law enforcement and have always worked cooperatively to help in their investigations. When the FBI requested information from us relating to this case a month ago we gave them all of the data in our possession and we will continue to support them with the data we have available,' Apple said in a statement.