Spokesman Henry Cambre told the Wall Street Journal the Coast Guard is testing the substance, which gives off a rainbow sheen resembling an oil spill. Test results were expected late Sunday.
On Saturday, Paul Barnard of the Coast Guard's New Orleans sector told The New Orleans Times-Picayune two calls came in about a suspected oil slick about 20 miles north of the site of last year's Deepwater Horizon disaster.
Officers confirmed the existence of a substance near the surface, but the investigation was cut short when their helicopter was diverted to a separate search and rescue mission. The Coast Guard later sent aircraft and boats from Mobile, Ala., and New Orleans to the scene.
Exploding whale video goes viral on Internet
Wisconsin business offering 'therapeutic cuddling' forced to close