Local paper says Belgian registered.
And according to
ASN Aircraft accident 02-SEP-2011 Blkow BO 208 C Junior D-EGFU (which has better credibility for me than any newspaper) it was D-EGFU.
But actually the paper says
The plane was registered to an airport in Belgium.
which is somewhat confusing. But the plane's operator CNE Air is based at Seppe EHSE, they show the machine on their own website.