BP workers in the Gulf of Mexico have stopped drilling a relief well and are preparing to evacuate the oil spill site as a tropical depression nears.

There is a 20-30% chance of tropical storm force winds (39mph or more) at the spill site by Tuesday, the National Hurricane Center says.

Because of the slow-moving vessels at the spill site, evacuation plans are already well under way.

Work on the relief well could be suspended for up to