(CBS News) ELMER'S ISLAND, La. - We may not have seen the last of Hurricane Isaac. Government forecasters said Thursday there's a 40 percent chance that remnants of the storm will form a tropical cyclone.
Isaac already has the Gulf of Mexico dealing with the remnants of an earlier disaster.
About 100 miles from the BP oil disaster spill site, there's a giant tar mat.
"It's about the length of a large bus, or three cars," said Garrett Graves, who oversees the ongoing BP cleanup for the state of Louisiana.
The tar mat is on Elmer's Island, a wildlife refuge. Louisiana has closed 13 miles of coastline and banned commercial fishing one mile off shore. This area was among the hardest hit during the original BP spill.
"BP has up to 1 million barrels of unaccounted oil in the Gulf of Mexico, and I think it will continue to manifest like this hurricane after hurricane for 10 to 20 years unless BP goes out and does a proactive cleanup effort," Graves said.
Four miles away, Keith Bergeron is worried about his charter boat business. Since Tuesday, he has found tar balls lying on Grand Isle's main beach.
"It hits you in the gut when you see it like this. It's one thing after another," Bergeron said.
An estimated 4.9 million barrels spilled from BP's runaway well, smearing the coastlines of four states. BP has spent $14 billion on its cleanup so far.
Mike Harrison, who directs BP's cleanup operations in Louisiana, said: "The vast majority of our cleanup activities have reached end points in most of the states. I do not believe that this is something that is hazardous nor humans should be concerned about."
State officials here say two weeks before Isaac hit, BP was ready to declare this beach cleaned up, and move on -- over Louisiana's objections. BP will get back to work in Louisiana on Friday.