According to reports, former Guantanamo Bay detainees were arrested near the Belgian city of Antwerp on terrorism charges. “We have dismantled a serious recruiting network for Syria,” a Belgian counterterrorism official said.

The two alleged terrorists are Moussa Zemmouri, 37, a Moroccan national born in Antwerp, and an Algerian man police identified as Soufiane A. Officials believe Soufiane A. spent time in Syria.

Officially, the two were arrested on charges of “participating in the activities of a terrorist group” and recruiting other extremist Muslims for terrorist activities overseas.

In addition, they were charged, along with three other men, with planning a burglary. They also reportedly possessed illegal weapons.

“They were in a car, we believe waiting to commit a robbery,” Jean-Pascal Thoreau, a spokesman for Belgium’s federal prosecutor, said.

The two spent time in Guantanamo between 2001 and 2005. Zemmouri was originally captured in the Kandahar region of southern Afghanistan, shortly after the September 11 attacks in 2001.

Freeing Zemmouri was the focus of several, ultimately successful, campaigns by anti-Gitmo groups. For example, Cage Prisoners, a group dedicated to exposing alleged “civil liberty violations” at the Guantanamo Bay prison, posted a profile of Zemmouri as a potential example of those alleged violations.

After repatriating to Belgium in 2005, Zemmouri wrote a book titled Innocent at Guantanamo, in which he maintains he holds no links to terrorism or terrorist networks.

Between 300 and 400 Belgians have gone overseas to fight for Islamist terrorist groups, such as ISIS and al-Qaeda. Recruiters for those extremist groups in Europe are the key to the rapid growth and outreach of the Islamists.

There are fears that returning militants could plot and execute massively destructive terrorist attacks on high-profile targets.

For President Obama, closing the Guantanamo Bay detention facility, which houses suspected terrorists, has long been a major goal.

Last Wednesday, the White House told reporters that it is in “the final stages of drafting a plan” to close the prison.

“It is a priority of the President. He believes it’s in our national security interest to close the prison at Guantanamo Bay,” White House Press Secretary Josh Earnest said in the daily press conference.

The Obama administration has yet to comment on the alleged terrorist arrests in Belgium.