The US Justice Department is investigating a potential crime related to the alleged funnelling of money to the White House in exchange for a presidential pardon, according to court documents unsealed in federal court.
On Tuesday, US District Judge Beryl Howell 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.
It said federal prosecutors in Washington said they 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 people acted as lobbyists to senior White House officials "without complying with the registration requirement of the Lobbying Disclosure Act".
A Justice Department official said no government official is or was a target of the investigation.
had to ask for Ms Howell's permission to view certain emails between a lawyer and clients, who were not identified.
Ms Howell granted the request in August, saying attorney-client privilege did not apply in that instance.
Prosecutors said they planned to confront three unnamed people with the emails and finish the investigation.
According to Ms Howell's order, government investigators said they seized "over 50 digital media devices, including iPhones, iPads, laptops, thumb drives and computer and external hard drives".
US Presidents enjoy wide latitude under the constitution in pardoning people convicted of federal crimes.
President Donald Trump last week pardoned his former national security adviser Michael Flynn, who twice pleaded guilty to lying to the FBI 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 Ms Howell's order, the Justice Department recently told her it wanted to keep the investigation from becoming public because it detailed "individuals and conduct" that had not yet been charged.
For this reason, the released document was heavily censored, or redacted. An excerpt seen by The Washington Post suggests that in the case of one individual, the investigation did not show that any "direct payment" had been made but that a presidential pardon could be linked to campaign contributions.
“[redacted] expected [redacted] to assist in obtaining clemency for [redacted] due to [redacted]’s past substantial campaign contributions [redacted] and [redacted]’s anticipated future contributions," the report said, referencing individuals who cannot yet be named for legal reasons.
The White House has not yet made a statement on Ms Howell's report, although on Tuesday Mr Trump appeared to address the investigation, tweeting, that the "pardon investigation" was “Fake News.”