Judicial Watch, a conservative watchdog group, announced on Thursday that it filed a Freedom of Information Act lawsuit against the FBI regarding records related to Peter Strzok, a top FBI counterintelligence agent who was part of special counsel Robert Mueller’s Russia inquiry team before being demoted due to critical messages about President Trump.

On Tuesday, the Justice Department delivered hundreds of messages between Strzok and his alleged mistress Lisa Page, a lawyer who had also been assigned to the probe. The messages reveal the two exchanged anti-Trump and pro-Hillary Clinton messages.

Strzok was reportedly removed from Muller’s team in August and moved to a human resources position after it was revealed he and Page “exchanged text messages during the Clinton investigation and campaign season in which they expressed anti-Trump sentiments and other comments that appeared to favor Clinton.”

Strzok was also a lead investigator in the investigation into Clinton's unauthorized private email server.

Judicial Watch filed the lawsuit after the FBI refused to respond to a FOIA request in August. Specifically, Judicial Watch seeks information pertaining to all records related to Strzok’s assignment to Mueller's team, which is investigating if the Trump campaign colluded with Russia during the 2016 election, and all records related to Strzok’s reassignment from Mueller’s team to another FBI position.

The watchdog group is also seeking employment forms and all records of communication between FBI officials or representatives.

“It is disturbing the FBI has stonewalled our request about the Mr. Strzok demotion for four months,” said Judicial Watch President Tom Fitton. “One can only conclude the FBI and Justice Department (including Mr. Mueller’s operation) wanted to hide the truth about how Strzok’s and Page’s political biases and misconduct have compromised both the Clinton email and Russia collusion investigations."