Two workers from an escalator contractor have been arrested following an incident at a Kowloon mall on Saturday afternoon that left shoppers injured. The men, aged 22 and 52, from Otis Elevator Company, were held on suspicion of handling mechanical parts subject to an inquiry into what happened at Langham Place. The pair, arrested for attempting to pervert the course of justice, were bailed and must report back next month. Earlier yesterday, the government ordered contractors to conduct extraordinary tests on 57 escalators more than 15 metres in height within a month. It comes after a faulty escalator suddenly reversed and injured 18 shoppers at the Mong Kok mall. Of the injured, two were still in hospital in a stable condition. One of them was a 47-year-old man, who was the most seriously injured. The Electrical and Mechanical Services Department said a damaged driving chain may have been the cause of the incident. A braking device on the 45-metre machine may have also malfunctioned. The chain couples the driving gear of an escalator with the wheels of itssteps. If the chain breaks, a safety device is expected to stop the machine from losing momentum. This will need to be investigated Charles Wong Kai-hon, escalator engineer “The department is conducting a thorough investigation to confirm the causes of the accident,” a spokesman said. Registered lift and escalator engineer Charles Wong Kai-hon said most escalators were equipped with a “non-reverse device” that could sense a loosening of chain tension and signal a set of auxiliary brakes to kick in. “If the main brake could not stop the escalator from going into reverse, the non-reverse device should have sensed it and given a signal to the auxiliary brake,” said Wong, a member of the Lift and Escalator Safety Advisory Committee. “In this case, it didn’t and this will need to be investigated.” Escalators were designed to be robust, and while issues of irregular chain tension were common, it was rare for chains to break off, he said. Wong said the city should shelve the practice of standing to one side as it encouraged people to walk up and down the escalator, increasing the risk of injury in accidents. “People should stand still and hold the handrails.” A spokeswoman for Langham Place said the escalator in question had not previously undergone any major repair work and had last been inspected on Thursday. No problems were found. The mall began inspections of all of its 40 escalators on Saturday night to ensure safety. It was not known when the entire inspection will be completed. The escalators were still cordoned off on Sunday. An Otis spokesman said on Sunday night that the arrest of the technicians came as “a surprise” and the company would defend them. He said the technicians were assisting the department, which then later called the police. “Our legal team is working with law enforcement to clarify the situation and we intend to defend our mechanics,” the spokesman said. A Langham Place spokesman said it would not comment on the arrest. Earlier on Sunday, according to Otis, the department had said its investigation would be focused on the escalator’s drive chain. In addition to its local team, Otis global escalator engineers were called in to assist with the investigation. The firm will also examine other escalators at the mall as needed.