Updated

Federal prosecutors brought the first criminal charges Tuesday in the Deepwater Horizon disaster, accusing Kurt Mix, a former BP engineer, of destroying evidence by deleting more than 300 text messages, including a finding that the blown-out well in the Gulf of Mexico was spewing far more crude oil than the company was telling the public.

Here are some questions and answers about Mix, the charges and the investigation.

Q: WHO IS MIX?

A: Mix, of Katy, Texas, was a drilling and completions project engineer for BP. He worked on estimating the amount of oil spewing from the blown-out well and was involved in efforts to stop the gusher, notably a procedure known as a "top kill." The "top kill" method involved pumping heavy mud into the well head to cap it. Though BP had high hopes it would work, it ultimately failed when the immense pressure of oil and natural gas escaping the well could not be overcome by the mud.

Q: WHAT IS MIX ACCUSED OF DOING?

A: Mix has been charged with two counts of obstruction of justice and faces up to 20 years in prison and a fine of up to $250,000 on each count. Specifically, he has been accused of deleting more than 200 messages sent to a BP supervisor from his iPhone in October 2010 containing information about how much oil was spilling out — and then erased 100 more the following year after receiving numerous legal notices from BP to preserve the information.

Mix was released on $100,000 bail. He surrendered his passport and can only travel between Louisiana and Texas. His next court appearance is scheduled for May 3. His attorney declined to comment after the hearing.

Q: WHY DID THE CHARGES COME TWO YEARS AFTER THE SPILL, AND WILL THEY IMPACT THE CIVIL SETTLEMENT?

A: The arrest is part of a criminal investigation launched June 1, 2010, by the Justice Department, a probe that is still ongoing. The charges are not likely to affect the proposed class-action settlement that would resolve more than 100,000 claims by people and businesses who blame economic losses over the spill.

BP PLC estimates it will pay about $7.8 billion to resolve these claims, but the agreement doesn't resolve any claims by the Gulf states or the Justice Department, which launched civil and criminal probes following the spill. A judge is set Wednesday to consider preliminary approval of the class-action settlement.

Q: ARE MORE ARRESTS EXPECTED?

A: It's not clear, but Attorney General Eric Holder said the "department has filed initial charges in its investigation," signaling more charges are likely to come. The Justice Department said the investigation into Mix and "other matters concerning the Deepwater Horizon disaster is ongoing."

David Uhlmann, a University of Michigan law professor who was chief of the Justice Department's environmental crimes section, said the charges are probably "just the first of what will be multiple criminal charges."

"It could be the sign that the government believes there was a more far-reaching cover-up about the size of the spill," he said.

Q: THE ARREST INVOLVED WHAT HAPPENED AFTER THE SPILL. WHAT ABOUT ANY WRONGDOING BEFORE THE EXPLOSION ON THE RIG?

A: During Congressional hearings in the months after the oil spill, executives of BP PLC and other companies working with them were grilled about what they knew and when before the explosion, so there is little doubt investigators are looking into this as well.