LONDON--BP Plc may permanently shut the well that caused the worst off-shore oil spill in U.S. history as early as Monday, the company said on Wednesday as speculation grew over the assets it might sell to cover mounting costs. Incoming BP chief executive, Bob Dudley, said the company would stay involved with the cleanup process in the Gulf of Mexico long after the leaking well was plugged and expressed optimism the damaged environment would recover. "It is possible that as early as Monday or Tuesday this well might be killed," Dudley said on National Public Radio. "There's no precision, there's nothing guaranteed. I'm hopeful and I do believe we've seen the end of oil flowing into the Gulf," he added. One hundred days after a rig explosion killed 11 workers and opened up an oil-spewing gash on the sea floor, criminal and civil investigations were examining whether BP and other companies involved misled both regulators and investors. "The investigation is ongoing ... there will be a criminal inquiry as well as civil investigation and it involves more than simply BP," U.S. Attorney General Eric Holder said in Cairo. The Washington Post said a "BP Squad" made up of several government agencies was conducting a criminal probe although it could be more than a year before any charges are filed. BP also faces a number of private lawsuits and claims for compensation from the spill that damaged fishing areas and tourist sites. The company expects to spend $60 million (38 million pounds) in advance payments in August, and has already handed out $256 million to those who have lost money because of the spill.