Police in the southwestern city Leshan have detained a 31-year-old man on the suspicion he caused an explosion on a bus Monday evening that injured 15, including himself.

In a statement early Tuesday morning, police said they had ruled out terrorism as a motive. The man, surnamed Gu, had previously been convicted for drug abuse and theft. The Leshan local was the only person who was seriously injured. The statement did not say what had caused the explosion.

Footage from a traffic surveillance camera showed that the bus had come to a stop and that passengers were getting off before the explosion occurred, shattering the bus’s windows. (Image: Weibo)