From the LA Times:

A team of top federal prosecutors and investigators has taken the first steps toward a formal criminal investigation into oil giant BP's actions before and after the drilling rig disaster off Louisiana. The investigators, who have been quietly gathering evidence in Louisiana over the last three weeks, are focusing on whether BP skirted federal safety regulations and misled the U.S. government by saying it could quickly clean up an environmental accident. The team has met with U.S. attorneys and state officials in the Gulf Coast region and has sent letters to executives of BP and Transocean Ltd., the drilling rig owner, warning them against destroying documents or other internal records.

The investigation is lead by Assistant Atty. Gen. Ignacia Moreno of the environment and natural resources division and Assistant Atty. Gen. Tony West, head of the DOJ's civil division. And, to underscore the scope of the investigation:

...the Obama administration has asked for $10 million to be set aside to pay for the investigation. President Obama, in a letter May 12 to House Speaker Nancy Pelosi (D- San Francisco), said the funding was needed "to hold BP, and other responsible parties in this spill, accountable for the crisis."

In a May 17 letter to Atty. Gen. Eric Holder, Senator Barbara Boxer asked him and his department to "review this matter with respect to civil and criminal laws related to false statements to the federal government." She cited many different assurances given to her by BP, including assurances that an oil spill would have little to no effect on fish habitats because the company would use "proven equipment and technology" to respond to a blowout & quickly contain the damage. As we all see now, this was absolutely not true.