Roughly 200 Belgians fighting for the Islamic State terrorist group in Syria may return to Europe to carry out attacks, Belgian officials announced Thursday.
Interior Minister Jan Jambon said intelligence services warned authorities that Islamist militants holding Belgian passports are "possibly coming back" with plans to strike, the Wall Street Journal first reported.
"From Belgium, there are a lot of Syria fighters, about 200 are still in Syria," Jambon said. "Our intelligence service said that we have to be aware that because of higher pressure in Syria, these people can come home so we have to detect them."
The European Union's top policing organization, Europol, announced earlier this year that close to 5,000 E.U. citizens who trained under ISIS had returned to Europe, forcing the continent to issue its highest terror threat in more than a decade.
Jambon said the threat of foreign fighters returning is a "permanent worry" for every European government, according to the Wall Street Journal.
His announcement arrived one month after the March 22 suicide bombings at Brussels Airport and the Maelbeek subway station that killed at least 35 people. ISIS claimed responsibility for the attacks.
One of the bombers was identified as Belgian citizen Najim Laachraoui, the bomb maker in both the Belgian and Paris terrorist attacks who trained with ISIS in Syria in 2013 before returning.
Jambon said he recently discovered that Laachraoui had worked at the Belgian airport he blew himself up in for five years prior to going to Syria, according to the Wall Street Journal.
"But we shouldn’t jump to conclusions, we know people get radicalized very quickly," he said, noting that there is no evidence Laachraoui had been radicalized while employed with the airport.
Background checks for employment at Belgian airports has since been tightened, he added.
Earlier this month, E.U. officials announced that Laachraoui held a cleaning position with the European Parliament during the summer for a month in 2009 and a month in 2010.