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(Updates with BP's latest estimate on spill size)
WASHINGTON, March 27 (Reuters) - More oil than previouslythought may have leaked into Lake Michigan this week from BPPlc's Indiana refinery, the company said on Thursday,after two U.S. Senators requested a meeting with the British oilmajor.
The request from Senators Mark Kirk, a Republican and DickDurbin, a Democrat, both from Illinois, came before BP issuedits estimate that between 15 and 39 barrels of oil had spilled -more than an earlier assessment that nine to 18 barrels leakedon Monday.
The Senators asked for details on the spill's cause, ananalysis of the impact of the 405,000 barrels-per-day (bpd)Whiting refinery's production increase, and information on whatis being done to prevent future spills.
"Given the Whiting refinery's recent expansion of itsoperations to double the amount of heavy oil sands beingprocessed, this spill raises questions about the long-termsafety and reliability of BP's new, expanded production," thesenators wrote to John Minge, chief executive officer, BPAmerica Inc.
The U.S. Coast Guard said on Wednesday that between nine and18 barrels had spilled. BP said on Thursdaythat the earlier estimate was based on the size of the sheen onthe lake's surface when the leak happened.
The company said the updated figure, which BP shared withthe Coast Guard and the U.S. Environmental Protection Agency,includes oil collected by vacuum trucks and an absorbent boom.
"BP is conducting further analysis to confirm thisestimate," the company said.
(Reporting by Ros Krasny in Washington and Kristen Hays andErwin Seba in Houston; Editing by Sandra Maler and Chris Reese)
