The FBI has seized the electronic data of a retired four-star general who authorities say made false statements and withheld “incriminating” documents about his role in an illegal foreign lobbying campaign on behalf of the wealthy Persian Gulf nation of Qatar.

New federal court filings obtained Tuesday outlined a potential criminal case against former Marine Gen. John R. Allen, who led U.S. and NATO forces in Afghanistan before being tapped in 2017 to lead the influential Brookings Institution think tank.

It’s part of an expanding investigation that has ensnared Richard G. Olson, a former ambassador to the United Arab Emirates and Pakistan who pleaded guilty to federal charges last week, and Imaad Zuberi, a prolific political donor now serving a 12-year prison sentence on corruption charges. Several members of Congress have been interviewed as part of the investigation.

The court filings detail Allen’s behind-the scenes efforts to help Qatar influence U.S. policy in 2017 when a diplomatic crisis erupted between the gas-rich Persian Gulf monarchy and its neighbors.

“There is substantial evidence that these FARA violations were willful,” FBI agent Babak Adib wrote in a search warrant application, referring to the Foreign Agents Registration Act.

Allen also misrepresented his role in the lobbying campaign to U.S. officials, Adib wrote, and failed to disclose “that he was simultaneously pursuing multimillion-dollar business deals with the government of Qatar.”

The FBI says Allen gave a “false version of events” about his work for Qatar during a 2020 interview with law enforcement officials and failed to produce relevant email messages in response to an earlier grand jury subpoena.

The 77-page search warrant application appears to have been filed in error and was removed from the docket Tuesday after The Associated Press reached out to federal authorities about its contents.

Allen declined to comment on the new filings. He has previously denied ever working as a Qatari agent and said his efforts on Qatar in 2017 were motivated to prevent a war from breaking out in the Gulf that would put U.S. troops at risk.

Allen spokesperson Beau Phillips told AP last week that Allen “voluntarily cooperated with the government’s investigation into this matter.”

Allen, who was a senior fellow at the Brookings Institution prior to becoming president, used his official email account at the think tank for some of his Qatar-related communications, the affidavit says.

Brookings did not immediately respond to a request for comment. Qatar has long been one of Brookings’ biggest financial backers, though the institution says it has recently stopped taking Qatari funding.

Olson was working with Zuberi on another matter involving Qatar in mid-2017 when Saudi Arabia, the United Arab Emirates and other Gulf countries announced a blockade of Qatar over its alleged ties to terror groups and other issues.

Shortly after the blockade was announced, then-President Donald Trump appeared to side against Qatar.

The court papers say Allen played an important role in shifting the U.S.’s response. Specifically, authorities say Allen lobbied then-National Security Advisor H.R. McMaster to have the Trump administration adopt more Qatar-friendly tone.

In an email to McMaster, Allen said the Qataris wanted the White House or State Department to issue a statement with language calling on all sides of the Gulf diplomatic crisis to “act with restraint.”

Federal law enforcement officials say then-Secretary of State Rex Tillerson did just that two days later, issuing a statement that called on other Gulf countries to “ease the blockade against Qatar” and asked “that there be no further escalation by the parties in the region.”

The Qatar Embassy did not immediately respond to a request for comment.

As part of the lobbying campaign, federal law enforcement authorities say, Olson and Allen traveled to Qatar to meet with the country’s ruling emir and other top officials.

At the meeting, Allen provided advice on how to influence U.S. policy and said the Qataris should “use the full spectrum” of information operations, including “black and white” operations, the affidavit says. “Black” operations are typically covert and sometimes illegal. Qatar has been accused of orchestrating hack-and-leak operations of its critics and rivals during the diplomatic crisis, including one targeting a UAE ambassador. Qatar has denied any wrongdoing.

Before they went to Doha, Allen wanted to “have a chat” with Olson and Zuberi about his compensation, the affidavit said. Allen suggested in an email that he be paid a $20,000 “speaker’s fee” for the weekend trip — even though he wasn’t giving a speech — and then later “work out a fuller arrangement of a longer-term relationship,” the affidavit says.

Zuberi paid Allen’s first-class airfare to Qatar, the affidavit said, but there’s no indication the speaker’s fee was paid. Allen’s spokesman said previously the general was never paid a fee. It’s unclear why. Some of Zuberi’s past business associates have accused him of not honoring his financial commitments.

Allen also had other financial incentives for helping the Qataris and maintaining strong ties to its top leaders, the FBI said.

“At the same time he was lobbying U.S. government officials on behalf of Qatar, Allen pursued at least one multimillion-dollar business deal with the Qatari government on behalf of a company on whose board of directors he served,” the affidavit says.

After returning from their trip to Qatar, Allen and Olson lobbied members of Congress, particularly those who supported a House resolution linking Qatar to terror financing, the FBI said.

Among them was Rep. Ted Lieu, a California Democrat who told law enforcement officials he didn’t recall exactly what Allen said but that his impression was he was there “to support the Qatari officials and their position.”