WASHINGTON (AP) — When a government document mysteriously appeared earlier this week in the highest profile case in the federal court system, it had the hallmarks of another explosive storyline in the Justice Department's investigation into classified records stored at former President Donald Trump's Florida estate.

The document purported to be from the U.S. Treasury Department, claimed that the agency had seized sensitive documents related to last month's search at Mar-a-Lago and included a warrant ordering CNN to preserve "leaked tax records."

The document remained late Thursday on the court docket, but it is a clear fabrication. A review of dozens of court records and interviews by The Associated Press suggest the document originated with a serial forger behind bars at a federal prison complex in North Carolina.

The incident also suggests that the court clerk was easily tricked into believing it was real, landing the document on the public docket in the Mar-a-Lago search warrant case. It also highlights the vulnerability of the U.S. court system and raises questions about the court's vetting of documents that purport to be official records.

The document first appeared on the court's docket late Monday afternoon and was marked as a "MOTION to Intervene by U.S. Department of the Treasury."

The document, sprinkled with spelling and syntax errors, read, "The U.S. Department of Treasury through the U.S. Department of Justice and the U.S. Marshals Service have arrested Seized Federal Securities containing sensitive documents which are subject to the Defendant Sealed Search Warrant by the F.B.I. arrest."

It cited a federal statute for collecting financial records in federal investigations. The document also included the two supposed warrants, one that claimed to be sent to CNN in Atlanta and another to a towing company in Michigan.

Those supposed warrants, though, are identical to paperwork filed in another case in federal court in Georgia brought by an inmate at the prison medical center in Butner, North Carolina. The case was thrown out, as were the array of other frivolous lawsuits the man has filed from his prison cell.

The man has been in custody for several years since he was found not competent to stand trial after an arrest for planting a fake explosive outside the Guardian Building, a skyscraper in Detroit. Since his incarceration, he has filed a range of lawsuits and has impersonated the Treasury Department, claimed to be a federal trustee and claimed to be a lawyer for the Justice Department, a review of court records shows.

In the Georgia case, the man alleged that Trump and others had "acquired 'millions of un- redacted classified tax returns and other sensitive financial data, bank records and accounts of banking and tax transactions of several million' Americans and federal government agencies," court documents say.

The judge in that case called his suit "fanatic" and "delusional," saying there was no way to "discern any cognizable claim" from the incoherent filings.

The man has repeatedly impersonated federal officials in court records and has placed tax liens on judges using his false paperwork, two people familiar with the matter told the AP. Because of his history as a forger, his mail is supposed to be subjected to additional scrutiny from the Bureau of Prisons.

It's unclear how the documents — the fake motion and the phony warrants — ended up at the court clerk's office at the courthouse in West Palm Beach, Florida.

A photocopy of an envelope, included in the filing, shows it was sent to the court with a printed return address of the Treasury Department's headquarters in Washington. But a postmark shows a Michigan ZIP code, and a tracking number on the envelope shows it was mailed Sept. 9 from Clinton Township, Michigan, the inmate's hometown.

The AP is not identifying the inmate by name because he has a documented history of mental illness and has not been charged with a crime related to the filing.

"There is simply nothing indicating that he has any authorization to act on behalf of the United States," the judge in the Georgia case wrote.

But despite the clear warning signs — including a stamp noting the Georgia case number on the phony warrants — the filing still made its way onto the docket.

Spokespeople for the Justice Department and the Treasury Department would not comment. They declined to answer on the record when asked if the document was false and why the government had not addressed it.

Representatives in the court clerk's office and the magistrate judge overseeing the search warrant case did not respond to requests for comment.

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Associated Press writers Eric Tucker and Fatima Hussein in Washington, Kate Brumback in Atlanta and Anthony Izaguirre in Tallahassee, Florida, contributed to this report.