BP said in a statement that the fire, which started after lightning struck the derrick  the familiar-looking tower used to lift the piping  was quickly extinguished, and there were no injuries. But as a precaution, the containment operation was shut down for about five hours.

Image President Obama and Gov. Charlie Crist of Florida walked along Casino Beach in Pensacola Beach, Fla., on Tuesday. Credit... Charles Dharapak/Associated Press

The containment cap is still the most successful method BP has had in collecting some of the oil that has been leaking from the undersea well, and it has only been partly effective. A series of attempts by BP to cap or plug the well before June 3 failed.

The new calculation of the flow of oil, if it holds up, suggests that BP’s latest plans for capturing oil will be adequate, if only barely.

BP had only able to collect about 15,000 barrels a day at its peak with the containment cap, but the company has outlined plans to deploy new equipment so that it can capture a minimum of 40,000 barrels a day by the end of June, and a minimum of 60,000 barrels a day by mid-July.

If the new range of flow estimates proves correct, and if BP is ultimately found guilty of gross negligence in actions it took that led to the Deepwater Horizon disaster, that would mean the company could be assessed fines of up to $258 million a day. Those fines could come on top of payments for cleanup costs and economic damage to Gulf Coast businesses.

Fearful that the spill could ultimately cost BP tens of billions of dollars, investors have driven the company’s market valuation down by 48 percent since the spill began, erasing $91 billion of shareholder value. BP shares rose more than 2 percent during regular trading on Tuesday, but then gave up all that gain and more in after-hours trading, following release of the new flow estimates.

In a separate development, BP started to make good Tuesday on a three-week-old promise, declaring that it would release $25 million to a group of universities to pay for research into the effects of the oil spill. The is the first installment of $500 million that the company has pledged for a research effort lasting a decade.