Balls of tar that floated ashore in the Florida Keys are not linked to the BP oil spill, but the Coast Guard is still on the lookout for contamination across the Gulf of Mexico.
Meanwhile, the U.S. State Department began "working level" talks with Cuba, Wednesday, to respond to the spill.
No signs of oil have been reported near Cuba, but officials say they want to be prepared.
"It is incumbent upon us to inform all of our neighbors, not just the islands, but those countries that could be affected by disasters that happen within our territorial waters," State Department Spokesman Gordon Duguid said.
The talks are a rare sign of cooperation with Cuba after more than 50 years of conflict between the two countries.
It's estimated 5,000 barrels of oil per day have been leaking into the Gulf as a result of an April 20 oil rig explosion near the Louisiana coast.
The blast killed 11 workers.