The US justice department is looking into claims that lobbyists have tried to use bribes to secure a presidential pardon, unsealed court papers show.
They say that in August investigators began investigating a "secret lobbying scheme" possibly involving attempts to contact White House officials.
The redacted filings do not give any names, but the justice department says no government official is being probed.
In a tweet, President Trump referred to the investigation as "fake news".
It is common for outgoing presidents to use their right to issue pardons, which wipe out convictions.
President Trump - who is due to leave office in January, although he is still contesting his election defeat in the courts - has used the procedure a number of times.
Last week he pardoned his former national security adviser Michael Flynn, who pleaded guilty to lying to the FBI.
Meanwhile, US media say Mr Trump has been discussing the possibility of pardoning family members.
What are the bribery claims?
The document released by a federal court in Washington DC on Tuesday relates to a request by the Department of Justice (DOJ) to use emails and other communications seized in a bribery-for-pardon inquiry.
The data, prosecutors say in the paper, points to potential "criminal activity".
They say individuals - whose identities are redacted - appear to have "acted as lobbyists to senior White House officials without complying with the registration requirements" for such activity.
Their aim, according to the papers, may have been to secure "a pardon or reprieve of sentence" for another unidentified individual.
According to the documents, prosecutors in August sought a court order "so that the investigative team [could] access" the communications and confront the suspects.
It is unknown who the people targeted were. On Tuesday the DOJ said: "No government official was or is currently a subject or target of the investigation disclosed in this filing."
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