A mainland tourist was subdued by commuters on a Tung Chung-bound train after she injured a woman with a knife yesterday afternoon, police said. The mental condition of the tourist, 28, who suffered cuts to her left hand and arm, was being assessed at Princess Margaret Hospital under police guard last night. The victim, 23, suffered injuries to her left arm, mouth and midriff and was being treated at the same hospital. Police said the women, who did not know each other, had a dispute on the train heading towards Lai King station from Nam Cheong, at about 3.30pm. 'The mainland woman was arguing with the Hong Kong woman on board the train,' a police officer said. 'During the dispute, the mainlander drew out a fruit knife and attacked the victim. She was subdued by other commuters.' An off-duty police officer on the train was alerted by the noise and a crowd surrounding the suspected attacker. He said he snatched the knife from the woman and put it in a bag he was carrying. A man on the Lai King platform said passengers fled from the women as the train arrived at the station. A spokesman for the MTR Corporation said a passenger pressed an emergency button and alerted the train driver to the incident, saying there was a dispute on board the train. He said MTR staff called police as one of the two women had said she was injured and needed hospital treatment. He said train services were not affected by the incident. A 20-centimetre knife was seized at the scene. Crime squad officers from Kwai Chung police station are investigating the incident.