The ex-British spy who wrote the so-called Trump dossier briefed FBI agents on his research at the beginning of July, much earlier than previously believed.

Weeks after the briefing with the retired spy, Christopher Steele, the FBI formally opened its investigation into possible ties between the Trump campaign and Russian government.

FBI director Jim Comey confirmed the existence and general date of the investigation during testimony in front of the House Intelligence Committee on Monday.

According to Yahoo! News, federal government sources said Steele briefed investigators on his findings on July 5. That was around two weeks after the ex-MI6 agent wrote the first of the 17 memos that make up what has been dubbed the Trump dossier.

BuzzFeed News published the 35-page dossier on Jan. 10. The document remains largely uncorroborated, and former intelligence officials in the Obama administration have recently cast serious doubt on it.

Michael Morell, the former acting director of the CIA and Hillary Clinton supporter, said last week that he was concerned about the accuracy of the dossier because Steele paid intermediaries who in turn paid sources for the information he used in the report.

But many Democrats appear to believe that the dossier contains accurate information. Several Democrats cited claims made in the dossier during Monday’s hearing. CNN did report last month that federal investigators have corroborated at least some information in the dossier, though not the most salacious claims.

Steele had written only one memo by the time he briefed the FBI on his findings. And that memo, which contains some of the most jarring claims in the dossier, relies heavily on a source of questionable background.

In the memo, dated June 20, Steele reported that the Russian government had been “cultivating” Trump for five years and that the Kremlin had been feeding Trump’s campaign “valuable intelligence” on political opponents, including Hillary Clinton.

One source for the memo claimed that the Russian government had video recordings of Trump with prostitutes in a Moscow hotel.

The source of that claim — labeled “Source D” in the dossier — has been identified as Sergei Millian, a Belarusian businessman who operates the Russian-American Chamber of Commerce.

Millian, whose real name is Siarhei Kukuts, appears to have overstated many of his claims about his business dealings with several companies. The Trump team has also denied claims Millian has made in several interviews that he helped set up real estate deals for Trump. Millian has refused to comment on the dossier since he was identified as one of its sources by The Wall Street Journal on Jan. 24.

Steele began researching Trump’s links to Russia after being hired by Fusion GPS, an opposition research firm working for Democratic operatives.

According to previous reports about Steele, the ex-spy eventually turned some of his research over to the FBI because he felt it was so inflammatory. He grew frustrated in the following months because he felt the FBI was not taking his reporting seriously. But the FBI came knocking for Steele again in October, according to The Washington Post. The paper reported earlier this month that the bureau struck an informal deal with Steele to continue his research.

Steele was never paid for his work, though it is unclear why. Iowa Sen. Chuck Grassley, the chairman of the Senate Judiciary Committee, has asked Comey to explain the arrangement with Steele. He is also questioning why the bureau was relying on research compiled by an investigator hired by a pro-Clinton operative.

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