Salah Abdeslam, a prime suspect in the Paris attacks, had documents about the German nuclear research center Juelich in his apartment in the Molenbeek area of Brussels, a group of German newspapers reported on Thursday.
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Juelich is near the Belgian border and atomic waste is stored there. The center said in a statement there was no indication of any danger and that it was in contact with security authorities and nuclear supervisors.
The Redaktionsnetzwerk Deutschland (RND) group cited sources within the parliamentary control committee, whose meetings are confidential, as saying Hans-Georg Maassen, head of Germany's domestic intelligence agency (BfV), had told the nine-person committee at the end of March that Abdeslam had the documents.
It said Maassen had told the committee, which is in charge of monitoring the work of German intelligence agencies, that printouts of articles from the internet and photos of Juelich chairman Wolfgang Marquardt had been found in Abdeslam's apartment.
RND said it was unclear whether Maassen had passed this information on to the chancellery or the interior ministry.
It said several members of the Bundestag lower house of parliament and a terrorism expert at the BfV said they knew of this information and Maassen had confidentially informed them.
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Neither the BfV nor the BND foreign intelligence agency were immediately available for comment when contacted by Reuters.
Abdeslam, who born and raised in Belgium to Moroccan-born parents, was arrested on March 18 in the Belgian capital and four days later, suicide bombers killed 32 people in Brussels airport and a rush-hour metro train.
Concerns that militants are turning their attention to the nuclear industry's weak spots have risen since the Brussels attack.