The storm knocked out power to around 7,500 homes as it passed by but all but a relative handful -- 150 customers -- had their electricity restored before Tuesday morning, a spokeswoman for the Bermuda Electric Light Co. said.

At 11 a.m. EDT (1500 GMT), what had been for a while the first hurricane of the 2008 Atlantic storm season was located around 260 miles (415 km) to the north-northeast of Bermuda and it was moving away at 12 miles per hour (19 km per hour), the US National Hurricane Center said.

Bertha had not strengthened back into a hurricane while clearing Bermuda, as the hurricane center had said might be possible, but it still had the potential to do so as it moved out over the open ocean. Tropical storms become hurricanes when their top sustained winds reach 74 mph (119 kph).

The Miami-based hurricane center said Bertha was likely to hold together as a hurricane or a tropical storm for several days as it moved northeastward on a track that ought eventually to take it to the hurricane graveyard of the North Atlantic.

Bertha at its peak became a "major" Category 3 hurricane on the five-step Saffir-Simpson scale of hurricane intensity.

Its surprisingly vigorous growth from a tropical storm and formation far in the eastern Atlantic, near Africa, so early in the six-month storm season could herald a busy summer. The Atlantic hurricane season, which begins on June 1, rarely gets into gear before August.

Oil markets have paid close attention to Atlantic storms since a series of powerful hurricanes in 2004 and 2005 toppled oil rigs and severed gas pipelines in the Gulf of Mexico, where the United States gets a third of its domestic crude supply.

On Tuesday, energy traders were keeping an eye on an area of disturbed weather between the Caribbean islands and Africa.

That area of low pressure had not developed overnight and conditions were becoming less favorable for it to grow into a tropical depression, the precursor to a tropical storm, the hurricane center said. (Reporting by Matthew Taylor in Hamilton, Editing by Michael Christie and David Wiessler)