During Bob Vylan’s set, the band’s singer Bobby Vylan (born Pascal Robinson-Foster) led Glastonbury crowds in chants of both “free, free Palestine” and, more controversially, “death, death to the IDF.”

U.K. police announced Monday that the weekend performances by rap punk duo Bob Vylan and Irish-language band Kneecap at the Glastonbury Festival are subject to a criminal investigation after they led crowds in chants calling for “death” to the Israeli military and chants of “Free Palestine.

A criminal investigation has been launched over performances by Bob Vylan and Kneecap at Glastonbury on Saturday, Avon and Somerset Police has said. The force said it had appointed a senior detective to investigate whether comments made by either act amounted to a criminal offence after reviewing footage.