A white high school teacher in Chicago has been suspended after being accused of hanging a stuffed Black football player doll on a string from a projector screen in his classroom. A Black history teacher saw the doll on Monday and confronted the white teacher, The Chicago Suntimes reports. The two educators then engaged in a heated argument in front of students.

Whitney Young Magnet High School Principal Joyce Kenner said Chicago Public Schools officials are now investigating the incident. Kenner addressed the community in an email, saying administrators and CPS Title IX office are working together “to not only investigate and respond, but to elevate student voice in the process.”

According to Kenner’s email, the white teacher “indicated” he had come across the doll in his room and “wanted the students to see if someone would claim it.” The principal also said “a colleague approached the teacher about the doll and the conversation between the two became contentious.”

“Our administrative team investigated the incident and spoke with the teachers,” Kenner said in the letter. “An official incident report has been created and filed with CPS.”

The district issued a statement, but didn’t identify the teacher.

“Chicago Public Schools (CPS) strives to foster safe and secure learning environments for our students, families, and colleagues. Our schools and the District investigate and address all complaints and allegations of wrongdoing in accordance with District policies and procedures,” CPS said in a statement to CNN, adding the teacher is suspended while the investigation continues.

The Chicago Teachers Union is urging Mayor Lori Lightfoot to make sure schools are safe for students and staff.

“Mayor (Lori) Lightfoot has a responsibility to provide a safe space for every member of our school communities, which is especially important in a district that serves a student population that is 90 percent Black and Brown children,” the union stated. “Any definition of ‘safety’ must include creating and reinforcing an environment of equity and inclusion for all students, staff and faculty of color.”