Bowing to public and Congressional pressure, Deputy U.S. Attorney General Rod Rosenstein appointed former FBI Director Bob Mueller on Wednesday to be a special counsel overseeing the investigation into Russian interference in the 2016 campaign, Justice Department officials said.

Mueller will take command of the prosecutors and FBI agents who are working on the far reaching Russia investigation, which spans multiple FBI field offices on both coasts.

"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 in a statement. "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 led the FBI for 12 years under Presidents George W. Bush and Barack Obama. He is second only to J. Edgar Hoover for longest tenure for an FBI chief.

Mueller has agreed to resign from his private law firm in order to avoid any conflicts of interest, the AG's office said.

More from NBC News:

Pressure builds as Congress calls Comey to testify

Three ways to hold an independent Russia inquiry

Sally Yates: 'There was nothing casual' about Flynn warning

The FBI, with the help of the Treasury Department, the CIA and other agencies, has been examining evidence of possible contacts, money transfers and business relationships between a variety of President Trump's associates and Russian officials, sources say.

The investigation goes well beyond a possible American connection, to include how Russian intelligence services carried out the campaign of fake news and leaking hacked emails that intelligence officials say was meant to hurt Hillary Clinton and benefit Trump.

But the question of whether Trump associates colluded with Russia is consuming public interest. No evidence has surfaced publicly linking Trump himself to the Russian interference effort.

Rep. Jason Chaffetz, R-Utah and the chairman of the House Oversight Committee, called Mueller a "great selection."

@jasoninthehouse: Mueller is a great selection. Impeccable credentials. Should be widely accepted.

The last special counsel was Patrick Fitzgerald, who was tapped in 2003 to investigate the leaking of a CIA operative's name.

Under Justice Department regulations issued in 1999, a special counsel is not fully independent of the Justice Department.

According to a Congressional Research Service report, the attorney general — or in this case, Rosenstein, since Attorney General Jeff Sessions has recused himself — must be notified of any specific actions the special counsel intends to take, and has the ability to countermand those proposed actions.

Modern special counsels have less independence than the special prosecutors employed during the Watergate investigations of the 1970s, who were appointed under a law that has now expired.