BP oil spill: Storm threatens recovery efforts
Workers at the Gulf of Mexico BP oil spill site are making final preparations to leave as a storm nears.
Work on the relief wells which BP hopes to use to permanently stop the leak is due to be suspended.
But incident commander Adm Thad Allen has allowed the damaged well to remain capped while the site is evacuated.
He said ships monitoring the sea bed for signs of problems will be the last to leave the site and the first to return.
"The seismic survey vessels, the acoustic vessels and the vessels operating the ROVs [remote-operated vehicles] will stay as long as possible," said Adm Allen.
"And if conditions allow it, they will remain through the passage of the storm."
Officials were preparing for the arrival of Tropical Storm Bonnie, due to reach the spill site on Saturday evening.
But the storm was downgraded to a tropical depression while crossing southern Florida late on Friday after winds dropped to about 35mph (56km/h).
"Bonnie could regain tropical storm strength as it moves across the Gulf of Mexico," the US National Hurricane Center said.
As of 0200 local time (2200 GMT, Friday) the centre of the depression was lying 125 miles west-south-west of Sarasota in Florida, the center said.
The storm has already caused flooding in Haiti, Puerto Rico and the Dominican Republic, but there were no reports of significant damage as it passed over Florida.
Storm warnings are in place for much of the coast of Louisiana, Mississippi, Alabama and southern Florida.
Much equipment, like the boom that has been laid offshore as a barrier to oil, is being moved to avoid damage from storm surges.
Production is being stopped at all eight of BP's oil and gas platforms in the Gulf.
Meanwhile, a technician who was on board the Deepwater Horizon rig when it blew up on 20 April has told investigators that alarms did not sound on the day because they had been intentionally "inhibited".
"They did not want people woken up at three o'clock in the morning due to false alarms," Mike Williams told an investigative panel from the US Coast Guard and Interior Department.
Rig-owner Transocean has issued a statement saying the alarm configuration was "intentional and conforms to accepted maritime practices".
At the spill site, Adm Allen said that the storm may disrupt the ships monitoring the well for 48 hours.
During that time, he said US Coast Guard planes would be watching for any leakage on the surface, and underwater microphones would record data for later analysis.
A "packer" - a plug used during storms - has been placed in the relief well to stabilise it while workers leave the site.
The Development Driller III and Development Driller II, which have been drilling the relief wells, and the Q4000 vessel, which was connected to the top of the damaged well, are all detaching and preparing to leave.
The captain of each vessel will decide when to leave the site and where to wait while the storm passes.
Adm Allen has said there is increasing confidence that the damaged well - closed with a new cap - can be left shut and unmonitored for several days.
The damaged well was closed off eight days ago while tests were being carried out to see if there were weaknesses in the well or ruptures in the sea bed.