Law enforcement authorities in the Samara region on Monday launched a criminal investigation into alleged “Nazi rehabilitation” after a group of recent high school graduates filmed themselves singing a patriotic Ukrainian song.

The regional branch of Russia’s Investigative Committee, which probes major crimes, said it uncovered “the illegal actions while monitoring social media.” It did not specify whether anyone was formally charged.

Media reports linked the police investigation to a video showing teenagers in the city of Tolyatti, about 1,000 kilometers (620 miles) southeast of Moscow, singing: “Our father is Bandera, Ukraine is our mother.”

Stepan Bandera, a World War II-era Ukrainian nationalist who briefly allied with Nazi Germany, remains a divisive figure. Hailed by some in Ukraine as a symbol of independence, he is portrayed in Russian state media as emblematic of what Moscow calls “Nazi ideology” in modern day Ukraine.

Since launching its full-scale invasion in 2022, Russia has effectively outlawed many Ukrainian national symbols, including the flag’s colors and the national anthem.

Police investigators in Samara said they are working to establish the full circumstances of the incident.

The charge of “Nazi rehabilitation” carries a maximum prison sentence of five years under Russian law.