New York prosecutors also are looking into President Donald Trump's inaugural fund. Photo / AP
A look at where the investigations related to US President Donald Trump stand and what may lie ahead for him:
What's this all about?
Special counsel Robert Mueller is looking into whether the Trump campaign coordinated with Russia and whether the president obstructed the investigation.
Trump also plays a central role in a separate case in New York, where prosecutors have implicated him in a crime.
They say Trump directed his personal lawyer Michael Cohen to make illegal hush-money payments to two women as a way to quash potential sex scandals during the campaign.
Democrat Jerrold Nadler, chairman of the House Judiciary Committee, announced the probe into possible obstruction of justice, corruption and abuse of power.
The panel is sending document requests to 81 people linked to the president and his associates.
The broad investigation could be setting the stage for an impeachment effort, although Democratic leaders have pledged to investigate all avenues and review Mueller's upcoming report before trying any drastic action.
"Over the last several years, President Trump has evaded accountability for his near-daily attacks on our basic legal, ethical, and constitutional rules and norms," Nadler said.
"Investigating these threats to the rule of law is an obligation of Congress and a core function of the House Judiciary Committee."
Trump dismissed the Nadler probe and others as futile efforts "in search of a crime."
On Twitter, the president exclaimed that it was "Ridiculous!"
Meanwhile, the Justice Department said career ethics officials had advised Attorney General William Barr that he should not recuse himself from overseeing the special counsel investigation — and Barr said he has decided to follow that advice.
Some Democrats had raised concerns that Barr might disrupt or upend Mueller's investigation.
Conservative author conspiracy theorist Jerome Corsi retracted an article he wrote last year for the website InfoWars alleging that Democratic National Committee staffer Seth Rich and his brother were involved in downloading and leaking DNC emails to the website WikiLeaks.
Seth Rich was killed in July 2016 in what Washington police believe was a robbery attempt.
On his website Corsi acknowledged that he did not have "independent factual knowledge" for the allegation and had instead relied on a Washington Times article that has since been retracted.
So did the Trump campaign collude with Russia?
There is no smoking gun when it comes to the question of Russia collusion.
But the evidence so far shows that a broad range of Trump associates had Russia-related contacts during the 2016 presidential campaign and transition period, and several lied about the communications.
There is evidence that some people in Trump's orbit were discussing a possible email dump from WikiLeaks before it occurred.
American intelligence agencies and Mueller have said Russia was the source of hacked material released by the anti-secrecy group WikiLeaks during the campaign that was damaging to Democrat Hillary Clinton's presidential effort.
What about obstruction of justice?
That is another unresolved question that Mueller is pursuing.
Investigators have examined key episodes such as Trump's firing of FBI Director James Comey and Trump's fury over Attorney General Jeff Sessions' recusal.
What does Trump have to say about all this?
The US President has repeatedly slammed the Mueller investigation as a "witch hunt" and insisted there was "NO COLLUSION" with Russia.
He also says Cohen lied to get a lighter sentence in New York.
When will it all wrap up?
It's unclear. Then-acting Attorney General Matthew Whitaker said in January that the probe is "close to being completed," the first official sign that Mueller's investigation may be wrapping up. But he gave no specific timetable.