A man attacked a bus used by a Japanese school in Suzhou, China, on Monday with what appeared to be a knife, seriously wounding a Chinese woman and injuring a Japanese woman and her child, according to an official at the Japanese Consulate in Shanghai.

The Chinese woman, who was aboard the bus, is in critical condition, while the injuries sustained by the Japanese woman and her preschooler child, who were waiting at a bus stop, are not life-threatening, the official said.

Asked whether strained ties between Japan and China could have been behind the attack, the official declined to comment, saying local authorities have already taken the man into custody and are investigating the matter.