Authorities are reportedly investigating a potential bias incident in the Hempstead Police Department.
Newsday says a white officer found a T-shirt with the words "KKK violate civil rights" above his locker Tuesday.
It comes amid years of racial tension within the department.
In 2007, a janitor found a noose in the locker room.
In 2011, a former lieutenant claimed she was demoted for filing gender and racial discrimination complaints.