The FBI's counterintelligence investigation into whether Trump campaign officials had improper contacts with Russia was triggered by information the bureau obtained about George Papadopoulos, a former adviser to the campaign, according to the memo released Friday by House Intelligence Committee Republicans.

Allies of President Trump have claimed the Russia probe began with the so-called Steele dossier that was paid for in part by Hillary Clinton and the Democratic National Committee (DNC). That would mean the Russia investigation itself - and by extension, special counsel Robert Mueller's probe - was launched from political opposition research.

But the memo states that FBI agent Pete Strzok opened the investigation in July 2016 based on "information" about Papadapoulos, rather than the dossier.

The New York Times has previously reported that Papadapoulos bragged to an Australian diplomat that the Russians had damaging information on Clinton before the hack of the DNC became publicly known. The Australian government tipped off the FBI to what Papadapoulos had said, according to the Times.

Papadopoulos has pleaded guilty to lying to the FBI and is cooperating with special counsel Mueller's investigation.

Still, the revelation that Strzok, who sent text messages disparaging Trump, launched the original investigation into the Trump campaign will further fuel debate over political bias at the FBI.

Strzok and Lisa Page, who is a lawyer at the FBI, exchanged private text messages during the campaign that were disparaging of Trump. Strzok and Page, who were having an affair, were both on Mueller's special counsel team at one point before being reassigned last year

Strzok was also a central figure in the investigation into Hillary Clinton's private email arrangement. Republicans, citing text messages between Strzok and Lisa Page, have said the FBI determined ahead of time to give Clinton an election year pass.

The memo released by Republicans on Friday, which was authored by staffers for House Intelligence Committee Chairman Devin Nunes (R-Calif.), also criticizes the FBI's use of the Steele dossier in a warrant application.

After the counterintelligence investigation began, the memo states, the FBI used the Steele dossier, in part, to obtain surveillance warrants for Trump campaign adviser Carter Page, who is not related to Lisa Page.

Then-FBI Director James Comey sought and received a warrant to spy on Carter Page in October 2016, the document states.

The surveillance applications typically involve several layers of authentication. Justice Department lawyers must show probable cause that the target of the Foreign Intelligence Surveillance Court warrant is acting as an agent of a foreign power.

The memo asserts that the FBI hid details about the origins of the dossier from the surveillance court. The memo also states that there is "not evidence of any cooperation or conspiracy between [Carter] Page and Papadopoulos."