in depth

Many experts believe oil from the Gulf of Mexico spill may have already entered into the ocean current which curls around the Florida peninsula, potentially taking the oil into the Florida Keys and possibly further up the US east coast.

Jane Lubchenco, the head of NOAA, said that since a southeastern tendril of oil from the slick was close to the Loop Current, it was likely to be swept up in the current, if it was not already.

"When that occurs, oil could reach the Florida Straits in eight to 10 days," she said.

'Unchartered territory'

Craig Cates, the mayor of Key West, said officials were "trying to keep a positive attitude" amid fears that the oil spill could be headed in their direction.

A Nasa satellite photo shows the spill spreading through ocean currents [Reuters/Nasa]

"We believe it is unlikely [the tar balls] are from the Gulf oil spill, but we'll know for sure in a couple of days," he said.

US Representative Ileana Ros-Lehtinen, whose district includes the Keys, said confirmation that the tar balls came from the spill would mean that Florida had entered "unchartered territory, with serious ramifications on our environment and economy."

The spill was caused by last month's sinking of the BP-operated Deepwater Horizon oil rig, rupturing the well and spilling thousands of barrels of oil into the sea every day.

BP, which has taken responsibility for cleaning up the spill, has said a 1.6km-long siphon tube inserted into the leaking well has managed to capture about 2,000 barrels per day from the leak.

That amounts to about 40 per cent of the 5,000 barrels (795,000 litres) BP has estimated to be leaking daily.

However, recently shot video footage showed vast amounts of oil continuing to spew into the ocean from the leaking well, underscoring the limited impact of BP's fix.