A report Wednesday that an investigation into alleged Russian interference in the 2016 election now includes an examination of whether President Donald Trump attempted to obstruct justice raises several legal implications.

The Washington Post, citing officials, reported Wednesday night that Robert Mueller, the special counsel now overseeing the investigation is looking at Trump's conduct.

The report states that an investigation into Trump for possible obstruction of justice began just "days" after the president fired FBI director James Comey, on May 9, citing people familiar with the matter. That would mean it began before Robert Mueller was appointed as special counsel by Deputy Attorney General Rod Rosenstein on May 17.

A spokesman for Trump's personal attorney Marc Kasowitz said in response to the Post report Wednesday: "The FBI leak of information regarding the President is outrageous, inexcusable and illegal."

According to the Post, which did not credit their reporting to an FBI leak, the special counsel is interviewing senior intelligence officials as part of the expanded probe, which previously focused on alleged Russian attempts to interfere in the election. The New York Times also reported Wednesday that Mueller wants to speak to at least "three high-ranking current or former intelligence officials."

If true, the expanded scope of the probe is a turning point, and raises several legal implications:

— An FBI inquiry of the Comey firing makes it more likely Rosenstein could be a witness, and thus potentially meet the parameters for recusing himself from overseeing Mueller's investigation.

President Donald Trump shakes hands with James Comey in the White House on Jan. 22. Andrew Harrer / Pool via Getty Images

Rosenstein told The Associated Press in an article published on June 3 that he would recuse himself if he were to become a subject of Mueller’s investigation.

"I've talked with Director Mueller about this," Rosenstein told the AP. "He’s going to make the appropriate decisions, and if anything that I did winds up being relevant to his investigation then, as Director Mueller and I discussed, if there’s a need from me to recuse I will."

Attorney General Jeff Sessions has already recused himself in the investigation because of his role in the Trump campaign.

— An obstruction inquiry reviewing Comey's firing makes it more likely that other government officials involved in that act, or related activity, could face legal exposure.

Federal employees interacting with the Trump administration regarding FBI staffing or this investigation, for example, may want to consider retaining counsel.

If the FBI is pursuing a theory that the Comey firing may be part of a larger obstruction effort, for example, then staff who knowingly assist with the original or related acts could face exposure. As a general matter, the Department of Justice can theoretically make an obstruction case against multiple people.

— This report asserts the obstruction inquiry began before Mueller took over.

Comey was fired on May 9, and Mueller was appointed on May 17. The suggestion is that the career FBI agents already determined obstruction warranted investigation, independently and before Mueller took over.

The White House initially said Trump acted on recommendations of Sessions and Rosenstein, which faulted Comey for his handling of the Hillary Clinton email investigation.

In an interview with NBC Nightly News' Lester Holt on May 11, Trump said he was going to fire Comey all along. Trump in that interview called Comey a "showboat" and a "grandstander" and said the FBI was in "turmoil."

But Trump also raised the Russia investigation, saying of the decision to fire Comey: "When I decided to just do it, I said to myself, I said you know, this Russia thing with Trump and Russia is a made up story. It’s an excuse by the Democrats for having lost an election that they should have won."

Comey said in a written statement before his testimony before the Senate Intelligence Committee last week that he told Trump he was not personally under investigation.

But Comey said at the hearing that he took Trump's alleged statement "I hope you can let this go" about former national security adviser Michael Flynn as a direction to end the investigation.

Asked if he thought the alleged comment was an attempt to obstruct, Comey said it wasn't for him to say, but "I'm sure the special counsel will work towards, to try and understand what the intention was there, and whether that's an offense."

Trump a day later said Comey's testimony vindicated him, and said in response to a question at a joint press conference: "No collusion. No obstruction. He's a leaker."

— As always, an FBI inquiry can be closed without charges, or lead to charges against a person or persons as determined by the prosecutor. Federal employees may face criminal charges while in office.

But the precedent is that the Justice Department takes the position that it cannot indict a sitting president.

And in the event an investigation were to find potential high crimes, the process is to refer such information or material to Congress, which the Constitution provides as the adjudicative body for alleged high crimes and misdemeanors by a president.

In other words, precedent has been that only the House — which is currently Republican controlled — may charge a sitting president with crimes, not the Justice Department.

Meanwhile, rumors raised this week that Trump was considering firing Mueller might, in theory, be put to bed now, since firing law enforcement leadership overseeing an investigation would look even worse if the president is reportedly under investigation.