BRUSSELS, Jan. 15 (Xinhua) -- An explosion hit a downtown neighborhood in the Belgian city Antwerp on Monday evening, completely destroying one building and severely damaging two others.

Firefighters said at least 4 people have received first aid but it is possible that other injured victims have already left the scene, or were taken to hospital by an ambulance.

"Explosion #Paardenmarkt could be 10 to 20 victims," the Antwerp police said on Twitter.

A Civil Protection unit is active at the scene of the explosion and is trying to locate possible victims under the debris, reported the newspaper DH (Derniere Heure).

The exact cause of the explosion is still unclear. Antwerp police added via Twitter that the explosion was not linked to terrorism in any way.