A bomb has gone off at the Brussels Institute of Criminology, without causing casualties, Belgian media say, the BBC reports.
Shortly before 02:30 local time (00:30 GMT), a car rammed through three fences, RTL Belgium reports.
“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.
Fire service spokesman Pierre Meys told Agence France-Presse that the “extremely powerful” blast “was probably not accidental”. Some 30 firefighters helped put out the resulting fire.
Prosecutors said an investigation was now under way.