Attackers rammed a car through the gates of a Brussels crime laboratory before starting a fire to destroy forensic evidence, prosecutors say.
Prosecutor's spokeswoman Ine Van Wymersch said a car broke through fences at about 02:00 (00:00 GMT).
She said there was "sensitive material" inside the laboratories, but it is not yet clear what if anything was destroyed in the fire.
Five people arrested nearby were later released without charge.
Initial reports in Belgian media said a bomb had exploded. But Ms Van Wymersch said that while a bomb was unlikely to have detonated, it was impossible to fully rule out that
Prosecutor's spokeswoman Ine Van Wymersch said a car broke through fences at about 02:00 (00:00 GMT).
She said there was "sensitive material" inside the laboratories, but it is not yet clear what if anything was destroyed in the fire.
Five people arrested nearby were later released without charge.
Initial reports in Belgian media said a bomb had exploded. But Ms Van Wymersch said that while a bomb was unlikely to have detonated, it was impossible to fully rule out that