Federal officials acknowledged on Thursday that the Gulf oil spill has substantially eclipsed the Exxon Valdez spill, making it the worst in U.S. history.
A scientific task force convened by the federal government says the spill estimate of 5,000 barrels a day that BP has been using is far off the mark. The task force says the true flow has been more than double that rate, and quite possibly more than five times that figure -- and this is a best-case scenario. They're still trying to come up with a figure that represents the most likely rate.
NPR's Richard Harris talks to Melissa Block about the estimates, and about BP's "top kill" effort to halt the leak. On Thursday, the company said the procedure seemed to be working.