A former employee at the Pinto Valley copper mine in Arizona is taking BHP Billiton Group to court over alleged discrimination.

Arizona District Court documents show that a summons has been issued to BHP Billiton and several of its subsidiaries along with the new owner of the mine, Capstone Mining Corp., which acquired the operation in 2013.

The plaintiff is Terry McGeachy, who — according to an Oct. 6 report by The Australian Financial Review — is identified as “African American” and was a heavy duty mechanic at the mine.

McGeachy is alleging that nooses were placed around his work areas on five occasions between 2012 and 2015 and a bottle and cup were used to create Ku Klux Klan symbols in a break room, according to the report.

He reportedly raised the issue with his superiors, but no investigation was initiated until after the fifth noose was found. There was no disciplinary action resulting from the investigation.

AFR reported that McGeachy was later found to be suffering from post-traumatic stress disorder and the matter is now being investigated by the U.S. Equal Employment Opportunity Commission.