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 in advance payments in August, and has already handed out $256 million to those who have lost money because of the spill.

MASSIVE CLEAN-UP

Although the flow of oil has stopped, there is still a massive clean-up operation that experts say will last for months. Although major oil slicks appear to have dispersed, experts are analyzing the extent of pollution in the sea.

An area of nearly 60,000 square miles (150,000 sq km) of Gulf of Mexico waters is closed to fishing and more than 600 miles of coastline in four U.S. states is affected by oil, according to the latest U.S. government reports.

The oil disaster has led to 2,239 days of beach closings, advisories and notices in the Gulf region, according to an annual beachwater quality report released on Wednesday by the Natural Resources Defense Council. It said the full impact of the disaster could last for years.

BP announced on Tuesday it had recorded $32 billion in charges for spill costs, and plans to sell $30 billion in assets to help pay for it.

Its shares were down 0.5 percent in morning trading on the New York Stock Exchange.

While multiple U.S. agencies investigate the spill, Congress is targeting BP through proposed energy legislation. Lawmakers could lift a cap on total liabilities, impose new safety rules and ban BP from getting new offshore oil exploration leases for up to seven years.

Dudley said the proposed bill appeared to be tailored for BP and warned that banning one of the country's largest employers in the Gulf of Mexico could have unintended consequences when unemployment is already uncomfortably high, standing now at 9.5 percent.

WHAT'S FOR SALE?

Sources with direct knowledge of the matter said BP was in talks with India's Reliance Industries and Essar to sell retail assets in Africa with an estimated price tag of $500 million.

Its Indonesian unit rushed to pre-empt speculation its assets there might be for sale.

In Indonesia, there is no change to our strategy and plans. Indonesia is an important area for BP, BP Indonesia president William Lin told Reuters.

Investment bankers said the assets BP could sell include its stake in Alaska's huge Prudhoe Bay oil field and its interest in Pan American Energy in Argentina, as well as smaller assets in Vietnam, Pakistan and Colombia.

The company has lost about 40 percent of its market value since the explosion.

The critical question remains what BP will look like two years from now, analysts at Morgan Stanley said.

Investors will need more clarity on the impact of asset sales and further reassurances of a cultural change regarding safety ... before BP can regain a multiple in line with its industry peers.

Industry executives said it was a good time to sell assets as relative stability in the oil price in the past nine months makes it easier for buyers and sellers to agree terms.

BP agreed to a $7 billion sale of oil and gas fields to Apache Corp last week, which valued the assets at around $19.40 per barrel of oil equivalent.

(Additional reporting by Muklis Ali in Jakarta, Matthew Lynley and Michael Erman in New York, Yasmine Saleh in Cairo and Rachelle Younglai in Louisiana; writing by Emily Kaiser and James Davey; editing by Will Waterman and Anthony Boadle)

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