CHIMAY, Belgium » One person was killed and at least four were injured in Belgium in an accidental explosion at a sports center near the French border.

Chimay police Chief Pierre Maton said early Friday that the blast was most likely “a gas explosion,” but an investigation into the cause was ongoing.

The blast in the town of Chimay, 75 miles south of the capital Brussels, happened just after midnight local time.

Several dozen police and firefighters were on the scene and the area had been cordoned off, but the damage was not as serious as initially feared. Windows were blown out of the two-story building, and one corner of the structure was badly damaged but there was no major collapse.

Firefighters were on the scene early Friday morning clearing the rubble and securing the building.

Police said they believed they have retrieved all the people from the rubble.

Chimay has a population of about 10,000 and is known for one of Belgium’s most famous breweries.