June 10 (Reuters) - United Auto Workers President Shawn Fain is under investigation by an independent federal monitor over allegations of retaliation against other union leaders, according to a court filing on Monday.

Monitor Neil Barofsky said he had opened an investigation in February to review allegations, including that the UAW secretary treasurer said she had faced retaliation for her refusal or reluctance to authorize certain expenditures for Fain's office, according to the filing. Barofsky also opened a probe into the secretary treasurer's actions. The UAW declined to comment. (Reporting by Nora Eckert and David Shepardson; editing by Jonathan Oatis)