A bomb exploded at the Brussels Institute of Criminology in the north of the Belgian capital on Monday but the building was empty and no one was wounded, broadcaster RTL said.
Brussels prosecutors confirmed that there had been an explosion at the institute and that there had been no casualties but said the cause had still not been determined.
A car rammed through the barriers at about 3 a.m. local time and one or more attackers exploded a bomb near the laboratories which caught fire, RTL said.
The institute is linked to the Belgian ministry of justice and carries out forensic investigations in criminal cases, it says on its website.
Europe has been on high alert after Islamic State attacks in Paris and Brussels over the past year.
(Reporting by Robert-Jan Bartunek; Editing by Nick Macfie)