BRUSSELS (AFP) - A explosion "of criminal origin" at Belgium's national criminology institute in Brussels early on Monday (Aug 29) caused a fire and major damage but no casualties, officials said.
Belgian media said the blast was caused by a car which rammed the building. "There was no one at the site" in the northern Brussels suburb of Neder-Over-Heembeek, a spokesman for the prosecutor's office told AFP, refusing to comment on the cause except to say the explosion had a "criminal origin".
The Belgian police have arrested five suspects over the blast overnight, prosecutors said. "Five people were arrested in the immediate neighbourhood... They are currently being questioned to see if they had any role in the incident," Ms Ine Van Wymersch, a spokesman for the Brussels' prosecutor's office, told a press briefing.
The prosecutor has set up a "crisis centre", the spokesman said. Fire service spokesman Pierre Meys said "it was probably not accidental".
"The explosion was extremely powerful," said Mr Meys. "Windows of the lab were blown out dozens of metres away."
He said about 30 firefighters were at the scene at around 3am local time fighting the blaze.
RTBF television said two suspects rammed a car into the institute grounds and threw an incendiary device at it.
The institute is part of Belgium's federal justice system. Among its tasks is to carry out scientific analyses linked to criminal cases and to study the functioning of the penal system.
Belgium has been high alert after suicide bombers struck Brussels airport and a metro station near the European Union headquarters on March 22, killing 32 people.
Those attacks were claimed by the Islamic State in Iraq and Syria (ISIS), which controls large areas of territory in Iraq and Syria and has claimed numerous terror attacks in Europe in recent months.
The militant cell responsible for the Brussels attacks was also heavily involved in the November Paris attacks in which 130 people were killed and hundreds more wounded.
The bombmaker for the Paris attacks, Najim Laachraoui, blew himself up at Brussels airport.
Earlier this month, it emerged that Belgian authorities were also hunting a cousin of the El Bakraoui brothers who also blew themselves up in the Brussels attacks.
Belgium has caught several people linked to the Brussels and Paris atrocities including Salah Abdeslam, the last surviving member of the Paris ISIS cell, who has since been extradited to France.
In June, the Belgian authorities approved a French extradition request for Mohamed Abrini, the "man in the hat" seen on CCTV footage with Laachraoui and Ibrahim El Bakraoui at Brussels airport.
Abrini has not yet been handed over pending further investigation into the Brussels attacks.