The blast occurred at an industrial estate near Ath, halfway between the Belgian capital Brussels and the French city of Lille, after reports of a gas leak.

Belgian officials initially spoke of 14 dead, then said only 10 had been confirmed, before Flahaut gave an updated toll. He said many of the injured suffered "serious burns".

"It was probably an accident," Flahaut told reporters in Ath, and said that an investigation was underway.

He said rescue workers were still looking for bodies inside a cardboard factory which burned down as a result of the blast, and officials said the toll may change.

Belgian King Albert II was scheduled to fly back from a foreign vacation to visit the region with Prime Minister Guy Verhofstadt.

WAR.WIRE