A faulty escalator at a Beijing subway station has killed a 13-year-old boy, badly hurt three passengers and slightly injured 24 others. Beijing MTR Corporation, which runs line four, has apologized for Tuesday morning's accident. The incident happened just after 9:30 am at exit A of Beijing Zoo Station. Witnesses say the rising escalator suddenly changed direction, caused more than 20 passengers to fall to the ground below. A 13-year-old boy, on the way to the zoo with his father and sister, was killed. His father and sister were injured. The company says it was launched an emergency response and all injured people are in hospital. Subway officials say the accident was caused by the escalator malfunctioning. The escalator, produced by the world's largest escalator firm OTIS, was still in guarantee, and the manufacturer had completed a routine check just last month. The government has demanded a probe into the accident and asked all subway operators to check their facilities. Ten escalators along the subway line have been suspended, and double checks are under way.