WASHINGTON -- When it comes to investigating Trump administration ties to Russia, the U.S. government has options.
U.S. intelligence agencies and Congress have pledged to probe Russia's involvement in the 2016 presidential election, and pressure on them to do so has grown after President Donald Trump fired his national security adviser, Michael Flynn, for providing inaccurate accounts of his conversations with the Russian ambassador before the inauguration.
Here's a look at the many ways the government could investigate itself:
THE FBI
The FBI is investigating Russian interference in the presidential election through the hacking of Democratic emails and likely is looking into possible contacts between Russian officials and Trump associates. The FBI has interviewed Flynn regarding his phone contacts with the Russian ambassador to the U.S. Flynn maintained for weeks that he had not discussed sanctions in the calls, but later conceded that the topic may have come up. If he lied to investigators, he would open himself up to a possible felony prosecution for making false statements.
Under the Obama administration, U.S. intelligence agencies said Russia interfered in the election with the goal of electing Trump. Trump has acknowledged that Russia hacked Democratic emails but denies it was to help him win.
STANDING COMMITTEE INVESTIGATIONS
The House and Senate intelligence committees are already examining Russian interference in the election. The Senate Armed Services Committee is also investigating.
But the congressional probes are ultimately in the hands of the Republican committee chairmen, and the standing committees already have agendas full with legislation and other issues. This has prompted Democrats and other groups to push for an independent investigation. Republicans say the three congressional reviews already underway are enough.
Sen. Dick Durbin, an Illinois Democrat, said on MSNBC on Wednesday that it's a "graveyard" for investigations when congressional intelligence committees get involved because their work is largely done outside of public view.
A SELECT COMMITTEE INVESTIGATION
Since standing committees have constraints on their time and resources, congressional leaders could also assemble a high-profile bipartisan panel of lawmakers from a variety of committees to examine Russian meddling. Select committees were formed to investigate such scandals as Watergate, the Iran-contra arms deal and more recently the Obama administration's handling of the deadly 2012 Benghazi attacks. But Republicans have so far refused to establish a select committee.
SPECIAL PROSECUTOR
Attorney General Jeff Sessions is facing pressure to step aside and appoint a special prosecutor for an independent investigation.
Outside counsel has been appointed in other major scandals, including Watergate and the Whitewater controversy involving Bill and Hillary Clinton. But while Sessions said during his confirmation hearings that he would appoint a special prosecutor to distance himself from any investigation involving Hillary Clinton's use of a private email server, he has given no indication that he plans to separate himself from investigations into Russian ties and Flynn.
Nothing requires him to appoint a special prosecutor. A statute mandating the use of independent counsel in certain situations was allowed to expire in 1999. Former Attorney General Loretta Lynch did not recuse herself from the Justice Department's investigation into the email practices of Hillary Clinton, a Democrat who would have been in a position to retain her if elected president.
INDEPENDENT COMMISSION
Democrats have also pushed for an independent commission consisting of people outside of Congress, such as former judges and law enforcement and military officials. Such a commission could subpoena documents and witnesses and hold hearings to examine Russian interference in the election.
Such commissions were formed to investigate the 9-11 attacks and the assassination of President John F. Kennedy.
