"The Deepwater Horizon Task Force is continuing its investigation into the explosion and will hold accountable those who violated the law in connection with the largest environmental disaster in U.S. history," said Holder.
In the complaint, Mix is accused of deleting text messages on two occasions "after being repeatedly informed of his obligation to maintain such records." Most of those messages were later retrieved, the Justice Department said.
In one thread, Mix allegedly deleted a string of some 200 messages that had to do with a process dubbed "Top Kill" that was aimed at stopping the spill.
"Too much flow-rate -- over 15,000" barrels of oil per day, Mix allegedly said in one text.
"At the time," the Justice Department noted, "BP’s public estimate of the flow rate was 5,000 BOPD -- three times lower than the minimum flow rate indicated in Mix’s text."
Moreover, BP "continued publicly to state that Top Kill was broadly proceeding according to plan," the complaint says.
"Before Top Kill commenced," the department added, "Mix and other engineers had concluded internally that Top Kill was unlikely to succeed if the flow rate was greater than 15,000 barrels of oil per day."
If convicted, Mix, a resident of Katy, Texas, faces a maximum penalty of 20 years in prison and a fine of up to $250,000 for each of the two criminal counts against him, the Justice Department said.
BP stated that, while it would not comment on the case against Mix, it has "clear policies requiring preservation of evidence in this case and has undertaken substantial and ongoing efforts to preserve evidence."
The company added that it "will continue cooperating in the Department of Justice's investigation."
The court document laying out the charges against Mix says that he began working with a BP team the day after the April 20, 2010, blowout. His initial estimates of the flow ranged from 64,000 barrels of oil a day to as much as 138,000.
It's clear that BP's own internal estimates were all over the place. A little more than a week later, the document says, Mix sent his supervisors a summary of the computer modeling, which showed the flow could be as low as 1,000 barrels a day to as high as 146,000.
Lawsuits have been filed seeking financial compensation from BP, and the oil giant has reached a tentative $7.8 billion settlement with thousands of individuals and businesses.
In addition, the U.S. government is expected to seek billions of dollars in environmental fines.
Tuesday's charges were the first against an individual in the blast that killed 11 workers and spilled 200 million gallons of crude into the Gulf of Mexico.
Mix resigned from BP a few months ago, the Justice Department stated.
Intellpuke: You can read this article by msnbc.com correspondent Miguel LLanos and NBC's correspondent Pete Williams in context here: usnews.msnbc.msn.com/_news/2012/04/24/11372699-engineer-first-to-face-criminal-charges-in-2010-bp-spill?lite