As BP watches its bill rise quickly for the oil spill, including $20 billion it is setting aside for claims, it could find the tally growing much faster in coming months if the United States Department of Justice files criminal charges against the company.

Based on the latest estimates, for example, the daily civil fine for the escaping oil alone could be $280 million. But criminal penalties, if imposed, could cause the costs to balloon still further, said David M. Uhlmann, a law professor at the University of Michigan, who headed the environmental crimes section of the Justice Department from 2000 to 2007.

Others note that such penalties could lead to loss of government contracts.

Even misdemeanor convictions under environmental laws could produce stunningly large fines under general federal criminal statutes, Mr. Uhlmann added. That is because the Alternative Fines Act allows the federal government to request twice the gain or loss associated with an offense if the Justice Department shows that a crime was committed.

Predictions by analysts of the overall cost of the spill to BP, when criminal penalties are included, have been rising. On Wednesday, Pavel Molchanov, an analyst at Raymond James, estimated the total legal cost, including criminal fines, at $62.9 billion, which would dwarf the $20 billion escrow account to be used to pay claims of economic loss.