Rain storms moving toward the Gulf of Mexico on Wednesday temporarily shut down undersea efforts to seal BP's ruptured well, interrupting work just as engineers get close to plugging the leak with mud and cement.
BP corked a relief tunnel deep beneath the sea floor to keep it from being damaged. The tunnel will be used to close up BP's leaky well, hopefully sealing it off for good.
BP vice president Kent Wells says the relief well was plugged Wednesday morning and drilling was halted.
Boat captains were told to clear out of the Gulf as a tropical storm system threatens the area.
Tom Ard, the president of the Orange Beach Fishing Association, says captains who showed up at docks to skim for oil Wednesday were sent home and told they wouldn't be going back out for five or six days because of weather.
Forecasters say a tropical weather system likely will move into the Gulf of Mexico over the weekend. It has a 50 percent chance of becoming a tropical depression or storm within the next 48 hours.
Scientists have been closely watching to determine if the cap is displacing pressure and causing leaks underground. If they can't observe the cap because of bad weather — for up to four days, Allen said — they could decide to reopen the cap to avoid missing signs the well is buckling.
In Florida, crews were removing protective boom intended to buffer the state's inland waterways in the Panhandle from oil. High winds and storm surge could carry the boom into sensitive wetlands, damaging those areas.
It could take several days to evacuate ships from the well site 50 miles off the Louisiana coast, where the BP-leased Deepwater Horizon rig exploded April 20, killing 11 and touching off one of America's worst environmental crises. Shell already has begun evacuating personnel not essential to producing and drilling on their operations in the Gulf.
President Obama's pointman on the disaster Thad Allen said an evacuation could delay operations as much as two weeks before work would resume to kill the well at the bottom.
Shell Oil, the U.S. arm of Royal Dutch Shell PLC, already has begun evacuating personnel not essential to producing and drilling on their operations in the Gulf.
BP crews are in the final stages of readying a relief tunnel before boring into the side of the ruptured well to dump heavy mud and cement, sealing it for good. BP also may pump mud and cement from the top, to make efforts at the bottom easier. That procedure, called a surface kill, would occur before the well is ultimately plugged from below.
Before talk of nasty weather, BP was inching closer to completion and had aimed for early August for the plug.
The well has spewed somewhere between 94 million gallons and 184 million gallons into the Gulf. BP has invested $4 billion on the spill so far.
The temporary cork in the well has helped cleanup efforts, and Allen said skimming vessels are starting to have trouble finding oil to collect. BP has about 1,600 boats operating daily in waters off Alabama, Florida and Mississippi, 600 fewer than last week, said Matt Kissinger, director of BP's "vessels of opportunity" program in the region.
Some boat captains, many earning more through the cleanup than they typically do from fishing, are worried it's a sign BP is leaving the Gulf too early.
Shrimper Minh V. Le of Bayou La Batre had both of his boats out skimming for oil initially, but one has been deactivated.
"A lot of us have put a lot of sweat into the program," he said. "You've got a 100-degree heat index, and there's a lot of wear and tear on our boats. If something breaks down it can cost $30,000. What they're paying isn't a drop in the bucket."