Joint efforts by rig operator BP, lead contractor SMIT, the US Coast Guard and US Department of Interior's Minerals Management Service had made significant progress in the last 24 hours. The structure is now nearly completely trim and all but residual water has been pumped out.

The 59,500-tonne rig has continued to rise and was stable, with the hull having reached normal displacement.

But concern for safety and the environment remained top priorities, and BP and SMIT continued to make the platform seaworthy and storm-safe as a precaution against the progress of Hurricane Emily into the western Gulf of Mexico.

Last week BP admitted Dennis wasn't to blame for the problems at Thunder Horse, which was evacuated as a precautionary measure and later found to be leaning more than 20 degrees. But an inspection of its hull and buoyancy pontoons found no structural damage, raising the possibility of human error.

The Thunder Horse project - in a Mississippi Canyon Block southeast of New Orleans – is not due to start production until the end of this year and subsea wells are not yet connected to the platform.