The U.S. Coast Guard now says an estimated 2,000 gallons of diesel fuel leaked from a ship in Government Cut.
A 95-foot tug boat containing about 7,800 gallons of diesel fuel was leaking into water off Miami Beach on Tuesday night.
Coast Guard officials said the initial report was that an estimated 100 gallons of fuel had leaked.
The spill has been determined not to be a threat to marine life or the beach shoreline.
It looked like a light screen in the water stretching from Government Cut around Fisher Island and near Star Island.
The ruptured fuel tank was patched and no more fuel is leaking. The vessel is moored at Dodge Island.
Crew members from the nearby Coast Guard station are assisting with cleanup efforts and monitoring for any possible shoreline pollution.
The cause of the leak is under investigation.