WASHINGTON — A senior FBI agent was removed from the staff of Russia special counsel Robert Mueller earlier this year after Justice Department investigators began reviewing whether the agent exchanged messages critical of President Trump, federal authorities said Saturday.

Peter Strzok, a top counter-intelligence agent who also helped run the investigation into Hillary Clinton’s use of a private email server, was abruptly reassigned this summer to the bureau’s human resources office after Justice’s inspector general discovered communications involving him and another FBI official, Lisa Page, who also had been previously detailed to Mueller's team.

The content of the communications was not immediately disclosed.

“Immediately upon learning of the allegations, the Special Counsel’s Office removed Peter Strzok from the investigation," Mueller spokesman Peter Carr said Saturday. "Lisa Page completed her brief detail and had returned to the FBI weeks before our office was aware of the allegations.”

The communications came to the attention of the inspector general during an ongoing inquiry into the handling of the Clinton email investigation by Justice and the FBI.

“The (inspector general) has been reviewing allegations involving communications between certain individuals, and will report its finding regarding those allegations promptly upon completion of the review of them,” the office said in a statement released Saturday afternoon.

When the communications were discovered, the inspector general alerted Mueller and other Justice Department officials.

The Justice Department, in a brief statement Saturday, said its officials were “aware of the allegations and are taking all appropriate steps.”

The disclosure, first reported by the Washington Post, comes a day after Mueller’s team announced it had reached a deal with former national security adviser Michael Flynn. Flynn agreed to plead guilty Friday for lying to the FBI about his contacts with Russian ambassador Sergey Kislyak and to cooperate with Mueller's ongoing inquiry into Russia’s interference in the 2016 campaign.

The development involving Strzok could revive claims by Trump that the Russia investigation is politically motivated. The president has frequently denounced the probe as a witch hunt, a hoax and fake news.

Trump insisted again Saturday that there was no collusion between his campaign and the Kremlin in last year's election. Mueller's team is investigating possible collusion as well as possible obstruction of justice.

"What has been shown is no collusion, no collusion," Trump told reporters Saturday. "There’s been absolutely no collusion, so we’re very happy."