By Anna Driver and Matthew Bigg
HOUSTON/VENICE, Louisiana (Reuters) - BP <:BP.LO:>Plc said on Thursday it was now capturing 5,000 barrels per day of crude oil leaking from its ruptured undersea Gulf of Mexico well, an advance in its efforts to contain the catastrophic spill.
Taking BP's own estimates, often repeated by its executives, this would mean it was now siphoning off virtually all of the oil from the month-old leak, which has unleashed an economic and ecological disaster on the U.S. Gulf Coast.
But many scientists have questioned BP's original estimate that the total size of the leak was about 5,000 barrels (210,000 gallons/795,000 litres) a day of oil.
BP spokesman Mark Salt said a mile-long (1.6 km) tube inserted into one of two known leaks from the well was "now capturing 5,000 barrels per day of oil".
Salt said the 5,000 bpd flow estimate had "always come" from the U.S. government National Oceanic and Atmospheric Administration. "Whatever the number, people can see we're trying to contain the flow and stop the spill," he added.
The company says it could begin injecting mud into the well as early as Sunday in an attempt to halt the gushing oil at the source.
The U.S. government, grappling with the oil spill disaster, said on Thursday it would not rely only on data given by well owner BP, but would make its own checks on the size of the leak.
With heavy oil sloshing ashore in Louisiana's fragile marshlands, heralding an ecological catastrophe, President Barack Obama's administration faces criticism that it has been too willing to accept BP's estimates of the gushing oil.
BP CEO Tony Hayward has been quoted recently by British media as playing down the size of the spill and its environmental impact.
"We're not depending on what BP is telling us," Interior Secretary Ken Salazar said on CNN in one of a series of television appearances.
'TAKING NOTHING FOR GRANTED'
Sceptics have questioned the data provided by the London-based energy giant, which is struggling to contain crude oil gushing from its seabed Gulf of Mexico well that blew out after the Deepwater Horizon rig exploded on April 20. The accident killed 11 workers.
Salazar said BP was responsible for damages so getting accurate data was essential.
"It's a grave and a very serious situation and we're taking nothing for granted," Salazar told NBC's "Today" show.
While other estimates have said the Gulf oil leak was far bigger, the company has defended the 5,000 bpd estimate as reasonable. "It's like a soda can, shaking it up and popping it off ... it's difficult to measure," BP executive vice president Robert Dudley told CNN, saying gas was escaping with the oil.
BP's shares had initially fallen nearly 3 percent in London trading, but then recovered.
(Additional reporting by Jeff Mason, Tabassum Zakaria, Vicki Allen, Tom Bergin Anna Driver, and Pascal Fletcher; Writing by Jane Sutton and Pascal Fletcher; Editing by Doina Chiacu)
