A security guard, who worked at a Belgium nuclear power plant, was murdered and his security badge was stolen, local media reported Saturday. The incident happened just days after suicide bomb attacks at the Brussels airport and on a metro killed at least 31 people and injured hundreds.

On Thursday, French language Derniere Heure newspaper reported that the suicide bombers, who blew themselves up on Tuesday, were originally targeting a nuclear site, but a series of arrests of suspect militants forced them to speed up their plans.

With the country on high alert, the report raised suspicions of the possibility that militants are seeking to get hold of nuclear material or planning to attack a nuclear site.

The security officer was murdered Thursday evening as he walked his dog in the Belgian city of Charleroi. When news of the killing emerged Saturday, the pass was quickly cancelled, according to reports.

Last year, a senior nuclear industry official was secretly filmed by jihadists, apparently with the intent of abducting him to obtain information about radioactive materials. Till now, 11 nuclear workers in Belgium had their work passes revoked after intelligence warnings.

According to the Telegraph, France has also stepped up security at many of its nuclear power plants, with workers being screened for Islamist sympathies.