DALLAS (AP) — The home arena of the Dallas Stars has launched an investigation into a video that apparently shows four fans celebrating a goal with a Nazi salute.

A spokesperson for the American Airlines Center told WFAA-TV in Dallas that the arena has “zero tolerance for any acts of hate and/or discrimination.”

“We strongly denounce the actions that appear to be depicted in the video footage and are conducting an internal investigation,” the spokesperson said. “All fans and attendees are expected to adhere to AAC and, as applicable, NBA or NHL Codes of Conduct when attending events.”

A Stars fan, Courtney Ripley, told the television station she took a 12-second video at a game against Toronto in late December. It shows four fans reacting to a goal by appearing to raise and extend their right arms with a straightened right hand facing downward. The video gained traction this week on several social media platforms.

A Stars spokesperson told ESPN on Thursday that the team is “fully aligned with the arena’s statement and working with them to find out exactly what happened.”