GRAND ISLE, La. —  An offshore oil rig has exploded in the Gulf of Mexico, west of the site of the April blast that caused the massive oil spill.

Coast Guard Petty Officer Casey Ranel says the blast was reported by a commercial helicopter company about 9:30 a.m. CDT Thursday. Seven helicopters, two airplanes and four boats are en route to the site, about 80 miles south of Vermilion Bay along the central Louisiana coast.

Ranel says it hasn’t been determined whether the structure is a production platform or a drilling rig or whether workers were aboard. Ranel says smoke was reported but it is unclear whether the rig is still burning.