BEIJING, June 4 (The New York Times) — A school security guard injured at least 39 people in a knife attack at a kindergarten in southern China on Thursday morning, state media reported. The motive remains unknown.

The attack was an eerie throwback to deadly attacks at schools in China over past years that prompted security upgrades and that authorities have blamed largely on people bearing grudges or who had unidentified mental illnesses.

The local government in the Guangxi region’s Cangwu county said 37 students and two adults suffered injuries of varying degrees in the attack.

Chinese state media identified the attacker as a security guard at the school surnamed Li. The suspect had been detained while an investigation was underway, they said.