Seven workers were injured last night – five of them critically -- when an oil rig exploded on Lake Pontchartrain, Louisiana. News sources say the Coast Guard is searching for one person who is still missing. All of the workers suffered blast-type injuries and burns.

The cause of the blast has not yet been determined. Also unknown: whether or not the incident spilled oil into the lake, a 630 square mile body of water located in parts of six different Louisiana counties.

The explosion occurred at 7:18 p.m. about 1½ miles from shore. The platform is owned by Clovelly Oil Co. 

"Authorities on the scene report that cleaning chemicals ignited on the surface of the oil rig platform," the City of Kenner Government posted on its Facebook page Sunday evening.