BRUSSELS: Belgian media say an explosion has rocked the nation's criminology institute in the capital Brussels.

State broadcaster RTBF reported Monday that a car forced its way into the site "before exploding a bomb" about 2 a.m. (0000 GMT). No source for the information was given.

RTBF says no one was injured but that damage at the site is significant.

Police have deployed in force and sealed off the area.

The institute assists and advises Belgium's justice authorities in carrying out their inquiries.

Belgium has been on high alert since a March 22 attack on the Brussels airport and subway killed 32 people.

Belgian police have arrested five suspects after a blast on Monday.

They said there was no immediate reason to believe there was any terror link -- Belgium is still on high alert after deadly Islamic State-claimed attacks in March -- and it could easily be a case of criminals trying to destroy evidence.

"Five people were arrested in the immediate neighbourhood... They are currently being questioned to see if they had any role in the incident," Ine Van Wymersch, a spokeswoman for the Brussels' prosecutor's office, told a press briefing.

"The possibility of a terrorist act is not confirmed," Van Wymersch said in a separate statement.

"It goes without saying that several individuals may have wanted to destroy evidence... An investigation is underway and several lines of inquiry are being considered," the statement said.

Van Wymersch said the crime lab, which gathers and analyses evidence, "was not chosen by chance; it is an important part of the justice department and deals with sensitive information in connection with several ongoing cases."

She said witnesses reported hearing several explosions but it was not yet clear how these were caused.

Press reports say a car was rammed through the gates and into the building which was set on fire, leading to several explosions in the lab.