WASHINGTON • The United States Justice Department is investigating a potential crime related to funnelling money to the White House in exchange for a presidential pardon, according to court documents unsealed in federal court.

US District Judge Beryl Howell on Tuesday released a heavily redacted order that described what she called a "bribery-for-pardon" investigation.

About half of the 18-page document was blacked out, with the publicly available version providing few details of the alleged scheme and naming none of the people potentially involved.

According to the document, federal prosecutors in Washington said they had obtained evidence of a bribery scheme in which someone "would offer a substantial political contribution in exchange for a presidential pardon or reprieve of sentence".

The order said prosecutors were also investigating a "secret lobbying scheme" in which two unidentified individuals "acted as lobbyists to senior White House officials, without complying with the registration requirement of the Lobbying Disclosure Act".

The Justice Department had to ask Justice Howell's permission to view certain e-mails between a lawyer and clients, who were not identified.

The judge granted the request in August, saying attorney-client privilege did not apply in that instance.

Prosecutors had said they planned to "confront" three unnamed individuals with the communications and finish their investigation.

According to Justice Howell's order, government investigators said they had seized "over 50 digital media devices, including iPhones, iPads, laptops, thumb drives, and computer and external hard drives".

A Justice Department spokes-man did not immediately respond to requests for comment.

Presidents enjoy wide latitude under the US Constitution in pardoning people convicted of federal crimes.

Last week, President Donald Trump pardoned his former national security adviser Michael Flynn, who had twice pleaded guilty to lying to the Federal Bureau of Investigation during the investigation into Russian meddling in the 2016 presidential election.

That was the first of what is expected to be a string of pardons in Mr Trump's final weeks in the White House.

According to Justice Howell's order, the Justice Department had recently told her it wanted to keep the investigation from becoming public because it detailed "individuals and conduct" that had not yet been charged.

Still, the unsealed documents offered a few clues about what the White House may have known about the scheme.

One passage appears to show that a lawyer for a convict had discussions with the White House Counsel's Office about a pardon or commutation, but it was unclear whether the discussions were part of the scheme or a normal back-and-forth with the White House about a convict's case.

Late on Tuesday, Mr Trump used Twitter to briefly address the disclosure of the investigation, calling it "fake news".

Investigators suspected the convict seeking the pardon was imprisoned as recently as this summer, and that two people working on behalf of the convict may have undertaken a secret lobbying campaign by approaching White House officials, according to the documents.

The two people may have offered to funnel money as political donations in exchange for the pardon or commutation, although it was unclear where the money was supposed to be sent.

Given Mr Trump's undisciplined approach to pardons, the disclosure - coming amid a flurry of reports about how he has been discussing whether to pardon his children and close confidants in the final weeks of his presidency - raised fears that the pardon process may have been corrupted.

Mr Trump has had talks with his personal lawyer Rudy Giuliani last week about a pre-emptive pardon for Mr Giuliani before he leaves office.

REUTERS, NYTIMES