The special counsel investigating Russia's election meddling is now reportedly looking at whether US President Donald Trump attempted to obstruct justice by firing the head of the FBI.
The Washington Post, citing several people who have knowledge of the investigation, said special counsel Robert Mueller's probe widened following James Comey's abrupt dismissal in early May.
Mr Comey has publicly accused Mr Trump of firing him to undermine the FBI's investigation into possible collusion between Mr Trump's 2016 presidential campaign team and Russia.
The White House quickly denied this was the reason, before Mr Trump himself confirmed it was true.
"I just fired the head of the FBI. He was crazy, a real nut job," Mr Trump told Russian officials when they visited the day afterwards, an official told the New York Times. "I faced great pressure because of Russia. That's taken off."
It's not clear how many people have been questioned by the FBI or the special counsel, or if Mr Trump will invoke executive privilege for himself or his officials to avoid answering questions - which could be illegal anyway, according to Supreme Court rulings made during the Watergate scandal.
Attorney-General Jeff Sessions refused to answer several questions when he appeared before the Senate Intelligence Committee earlier this week, saying Mr Trump might want to invoke executive privilege about their conversations - which he hasn't yet done.
Mr Comey last week told the same committee there was no FBI investigation of Mr Trump himself in regards to Russia, at least under his leadership. The Post suggests Mr Comey's "carefully worded comments" could mean the investigation into Mr Trump began soon after Mr Comey was fired.
It emerged last week Mr Comey leaked a memo he wrote after meeting Mr Trump to a friend in the media, to combat Mr Trump's claims about the pair's conversations.
"The FBI leak of information regarding the President is outrageous, inexcusable and illegal," a spokesperson for Mr Trump's personal lawyer told the Post.
The special counsel declined to comment on the Post's report.
Mr Trump has repeatedly called the Washington Post's reporting "fake news".
The report came on Mr Trump's 71st birthday.
Obstruction of justice was one of the crimes Richard Nixon was accused of when the impeachment process began against him. He resigned before he could be impeached.