Early warning systems on the Deepwater Horizon rig had been switched off, a federal investigation has been told.
Michael Williams, a chief technician at Transocean, the firm that operated the doomed rig for BP, told a federal panel in New Orleans that alarms had been disabled to prevent workers being woken up by false alarms.
He said he had protested to his supervisor, Mark Hay, a year before the explosion that destroyed the rig, but was told the alarm system had been "bypassed" on Transocean's "entire fleet".
His claims were made as the rigs, ships and other vessels in the Gulf of Mexico began to scatter to avoid the worst effects of a tropical storm that could hit as early as today. The storm made landfall in Florida yesterday and is forecast to pick up strength crossing the Gulf.
The evacuation was sanctioned by US authorities even though it will delay by as much as two weeks efforts to complete the two relief wells that promise finally to seal the gusher for good. "Preservation of life and preservation of equipment are our highest priorities," said Admiral Thad Allen of the US Coast Guard.
The rigs that were drilling relief wells, one of which had been on schedule for completion perhaps early next month, were hastily drawing up a mile of pipe before departing the area for safer waters.
Tropical Storm Bonnie, the second named disturbance of this year's hurricane season, was expected to pack winds of between 39 and 73 miles per hour by the time it nears the coast of Louisiana.
The approaching storm also prompted the Governor of Louisiana, Bobby Jindal, to announce a state of emergency last night. He said that officials along the coast would be ordering the evacuation of low-lying areas ahead of possible flooding from an expected storm surge.
BP expressed confidence that the new cap containment device that finally stopped the oil from leaking into the ocean last week would hold firm during the storm. The cap is one mile beneath the ocean's surface. For a while, however, the eyes and ears of BP at the site may be lost if the ships that operate the robots, cameras and listening devices on the seabed are also forced to leave.
Those ships with the submersible robots on deck will be the last to depart, however, and if Bonnie is less severe than expected, may be able to remain. If it does become necessary to withdraw them and all the surveillance equipment then only satellite images would notify BP in the event of the cap failing and the flow of oil resuming.
Analysts predicted that the UK-based energy giant may post a second-quarter loss of $13bn (£8.4bn) reflecting the clean-up and containment costs and provisions made to answer financial claims against it.