HOUSTON/LONDON,  (Reuters) – The approach of a major  storm yesterday forced BP Plc to halt efforts to permanently  plug a gushing oil leak in the Gulf of Mexico, sending ships  and workers retreating to safety.

Two rigs stopped drilling the relief wells intended to halt  the leak for good and prepared to move out of the storm’s path.  Tropical Storm Bonnie weakened to a tropical depression after  moving across Florida yesterday.

But Bonnie could strengthen again as it feeds off warm Gulf  waters. “Bonnie could regain tropical storm strength as it  moves across the Gulf of Mexico,” the Miami-based hurricane  National Hurricane Center said.

The storm has been on a track expected to take it over the  site of BP’s oil spill this afternoon.

Many non-essential workers abandoned the spill site, and  officials said key ships would likely pull out later yesterday  and be gone about two days.

Ships collecting seismic and acoustic data on the capped  well and those operating underwater robots that provide a live  feed of the wellhead would be the last to leave, and could stay  if seas do not become too rough, officials said.

“If we have to evacuate the scene we’re probably looking at  a very limited window — probably 48 hours,” said retired Coast  Guard Admiral Thad Allen, the top U.S. spill official.

BP sealed the leak last week with a tight-fitting  containment cap, choking off the flow of oil for the first time  since an April 20 rig explosion killed 11 workers and sent  crude spewing into the Gulf, soiling coastlines in five states  and devastating tourism and fishery industries.for completing a  relief well that would permanently plug the leak to late  August. But the ruptured well will remain capped, easing fears  the flow would resume.

The evacuation also delayed another potential solution, the  launch of a “static kill” operation to pump heavy drilling mud  and possibly cement into the well.

BP said it was shutting down production at its eight  company-operated platforms in the Gulf in preparation for a  full evacuation of workers.

The U.S. government said 28.3 percent of Gulf oil  production and 10.4 percent of Gulf gas output by all companies  had been shut ahead of the fast-moving storm.

Allen said the storm could have benefits and drawbacks for  containment efforts. Heavy waves and tidal churn could help  break up the oil, but high winds and waves could drive it  deeper into wetlands and coastal areas.

“In some scenarios it might actually be good for cleansing  the system, but in other circumstances it might cause even more  problems if it blows a lot of the oil directly onshore,” said  Chuck Kennicutt, a professor at Texas A&M University who  studied the 1989 Exxon Valdez spill in Alaska.