The DOJ has been investigating the shooting as an act of terrorism.

More than 20 Saudi students are expected to be expelled from the U.S. amid an ongoing investigation into the Saudi military officer who killed three sailors and wounded eight others at the Naval Air Station in Pensacola last month, an administration official told ABC News Monday.

While the trainees identified by investigators are not expected to be accused of directly aiding Lt. Mohammed Alshamrani in his alleged attack, a review launched by the FBI found that several of the students failed to report concerning behavior the Alshamrani was exhibiting, other trainees who had engaged with extremist groups online, and several who were found to have possessed child pornography, according to the official.

Attorney General William Barr and FBI Deputy Director David Bowdich will hold a news conference Monday afternoon to provide an update on the investigation of the Pensacola shooting and the ongoing review of the Saudi military training program.

Following the shooting, the Pentagon announced a ban on operational training for 852 Saudi students on U.S. bases, though classroom instruction for the students continued after a DOD “screening” of all Saudi military students training at US bases found “no information indicating an imminent threat.”

However, a senior defense official at the time cautioned that it was a screening tool, not an investigative tool, and so it was not possible to draw wider conclusions about what Saudi students may have known about the Dec. 6 attack. There are a total of 272 international military students at Pensacola from a number of countries.

“I have signed out directives that address enhanced screening of all of our foreign students, that address credentialing going forward, weapons policies, et cetera,” Defense Secretary Mark Esper said in an interview with CBS’ “Face The Nation” on Sunday when asked about the planned expulsions.

“I think we’re being very careful,” National Security Adviser Robert O’Brien said Sunday in an appearance on “Fox News Sunday.” “Obviously Pensacola showed that there had been errors in the way that we vetted, and I think out of an abundance of caution Secretary Esper’s taking these actions to protect our service men and women.”

Former acting undersecretary for intelligence at the Department of Homeland Security John Cohen said the circumstances surrounding the shooting reflect the broader challenges faced by the Pentagon in vetting foreign military personnel who attend training inside the U.S.

“Foreign military personnel need to be vetted not only as they are traveling to the U.S. but also on a recurrent basis throughout their stay,” Cohen, an ABC News contributor, said Monday. “Vetting procedures also need to be updated regularly so that they take into account an evolving threat environment.”

Barr and Bowdich are also expected to speak about ongoing efforts by investigators to seek Apple’s help in unlocking two iPhones owned by the alleged shooter. ABC News confirmed last week that FBI General Counsel Dana Boente sent a letter to the company saying investigators were not successful in their efforts to crack the passcodes for the phones, which they said Alshamrani sought to destroy during the shooting.

Barr’s announcement Monday comes as the FBI has been treating the case as a presumed act of terrorism. .

A joint intelligence bulletin released shortly after the shooting showed that the shooter wrote the phrase “the countdown has started,” on Sept. 11, 2019, and that Alshamrani referred to non-Muslims as “infidels” and defended jihad.

“I’m against evil, and America as a whole has turned into a nation of evil,” one post read, according to the report. “What I see from America is the supporting of Israel which is invasion of Muslim countries, I see invasion of many countries by its troops, I see Guantanamo Bay. I see cruise missiles, cluster bombs and UAV.”

The bulletin also offered more details about the shooting, saying that the shooter purchased the gun through a hunting exemption for foreign nationals and detailed that the shooter fired shots directly at photos of President Trump and another unnamed president.