Crews work on trying to stop oil leak in the Gulf
It could take hours or it could take months to stop a 42,000-gallon-a-day oil leak polluting the Gulf of Mexico at the site of a wrecked drilling platform.
Whether the environmental threat grows many times bigger depends on whether the oil company involved can turn the well completely off.
Crews are using robot submarines to activate valves at the well head in hopes of cutting off the leak, which threatens the Gulf Coast's fragile ecosystem of shrimp, fish, birds and coral.
If the effort fails, they'll have to start drilling again.
A spokesman for BP PLC says the work will take 24 to 36 hours, and there's no guarantee of success.
For the second consecutive day yesterday, high waves prevented boats and equipment from going out to clean the spill.
Airplanes sprayed chemicals to break up the oil.
The spill is still about 70 miles from the mainland.