The Justice Department has appointed former FBI Director Robert Mueller to be a special counsel to lead the investigation into Russian meddling in the 2016 campaign.

Deputy Attorney General Rod Rosenstein made the announcement Wednesday evening, just over a week after President Trump suddenly fired FBI Director James Comey, whose agency was probing whether Trump has any ties to Russia.

The Justice Department said the White House was informed of the decision to appoint Mueller, who was FBI director for 12 years under Presidents George W. Bush and Barack Obama, after the order had been signed.

"In my capacity as acting attorney general, I determined that it is in the public interest for me to exercise my authority and appoint a special counsel to assume responsibility for this matter," Rosenstein said.

"My decision is not a finding that crimes have been committed or that any prosecution is warranted. I have made no such determination. What I have determined is that based upon the unique circumstances, the public interest requires me to place this investigation under the authority of a person who exercises a degree of independence from the normal chain of command."

Mueller issued a brief statement from the WilmerHale law firm in D.C. "I accept this responsibility and will discharge it to the best of my ability," he said.

Rosenstein, who was in charge of the Russia investigation since Attorney General Jeff Sessions recused himself, said a special counsel was chosen to maintain the confidence of the American people.

"Each year, the career professionals of the U.S. Department of Justice conduct tens of thousands of criminal investigations and handle countless other matters without regard to partisan political considerations. I have great confidence in the independence and integrity of our people and our processes," Rosenstein said.

"Considering the unique circumstances of this matter, however, I determined that a Special Counsel is necessary in order for the American people to have full confidence in the outcome. Our nation is grounded on the rule of law, and the public must be assured that government officials administer the law fairly.

"Special Counsel Mueller will have all appropriate resources to conduct a thorough and complete investigation, and I am confident that he will follow the facts, apply the law and reach a just result."

Rostenstein's statement echoes calls by lawmakers on both sides of the aisle for a special prosecutor. This week, a memo that Comey reportedly wrote after he met with Trump in February says the president wanted Comey to lay off investigating Trump's former national security adviser, Mike Flynn.

This suggests Trump may have tried to influence the federal Russia probe, and some lawmakers have taken notice. Rep. Justin Amash, R-Mich., said the memo could lay the grounds for impeachment, if it exists.

The Senate Intelligence Committee has asked the FBI to provide copies of any notes or memos written by Comey. It also sent a letter to Comey himself, asking him to testify in "both open and closed sessions."

The Justice Department's move was applauded by House Oversight Committee Chairman Jason Chaffetz, R-Utah, Wednesday night.

Top Democrats, including House Oversight ranking member Elijah Cummings, D-Md.; and Sens. Dianne Feinstein, D-Calif., and Jeff Merkley, D-Ore., also say they support Mueller's appointment.

Senate Minority Leader Chuck Schumer, D-N.Y., said Rosenstein "has done the right thing."

"Former Director Mueller is exactly the right kind of individual for this job. I now have significantly greater confidence that the investigation will follow the facts wherever they lead," Schumer said in a statement.

The Justice Department said Mueller has agreed to resign from his private law firm to avoid any potential conflicts of interests.

Mueller became President George W. Bush's director of the FBI one week before the Sept. 11, 2001, terrorist attacks.