A bomb has gone off at the Brussels Institute of Criminology, without causing casualties, Belgian media say.
Shortly before 02:30 local time (00:30 GMT), a car rammed through three fences. "One or more" suspects then reportedly detonated a bomb near the laboratories.
Belgium's terror alert level remains high since bomb attacks on Brussels airport and the city's metro, claimed by so-called Islamic State that killed 32 people in March.
It is unclear what happened to the suspects behind the latest blast, which Belgian media said had caused "significant" damage. Forensic analysis linked to criminal cases is carried out at the site, but it is not the only laboratory of its kind linked to the police.
The independent institute, linked to Belgium's federal justice body, is in Neder-Over-Heembeek, a suburb in the north of Brussels. Bilal Hadfi, who blew himself up outside the Stade de France during last November's Paris attacks, lived in Neder-Over-Heembeek.