MINDEN, La. (AP) — A state police spokesman says nighttime fog and moisture in the ground were two of the reasons why it took a while for authorities to confirm the source of an explosion that rattled Webster Parish.

That blast happened late Monday in an underground bunker at Explo Systems Inc, at the Camp Minden industrial site.

State police Troop G spokesman Matt Harris said an investigation by the hazardous materials unit is under way. As for why no one could confirm the source of the blast until early Tuesday, Harris said in The Times of Shreveport reports that the blast site was not easily visible due to darkness and fog. He added that moisture in the ground because of recent rains allowed the explosives to burn out quickly.