Gulf cleanup effort is complete, but the question remains: What caused the oil slick in the first place?

Gulf cleanup effort is complete, but the question remains: What caused the oil slick in the first place?

Federal authorities say efforts to clean up an oil slick in the Gulf of Mexico are approximately 85% complete, though officials are still trying to determine the origin of the spill. Containment actions in the Gulf where the hydrocarbon plume was initially detected have concluded and no residue remains, officials say. More than 90 tonnes of waste impregnated with oil have been collected from beaches in the municipality of Coatzacoalcos, Veracruz…