BEIJING - China's top quality watchdog has ordered all escalators that are similar to the one involved in a tragedy in the capital this week that took the life of a 13-year-old boy to be put out of use and overhauled.

The organization made the move after an escalator at a subway station reversed direction on Tuesday, causing people to fall.

"Preliminary investigation concluded that the OTIS model has a design defect and was not maintained well during the last regular check," said Zhang Juming, a spokesman from the Beijing bureau of quality and technical supervision, during a news conference.

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Zhang added that a similar incident in which an escalator suddenly reversed direction took place in Shenzhen, in South China's Guangdong province. It too was the same model - OTIS 513 MPE. The General Administration of Quality Supervision, Inspection and Quarantine called on local inspection authorities to carefully check any escalators of the same type.

It is not known how many escalators of that model are in use across the nation but there are 257 of them in the capital alone within the subway system.

Zhang said two bolts within the escalator's engine failed, causing the accident.

One of the bolts fell off while the other broke, making the driving engine shift position and fall off the chain belt. With the escalator effectively without power, it reversed direction because of gravity.

No representative from the OTIS Elevator Company attended the news conference.

An OTIS manager on Wednesday told Beijing Times that regular checks are carried out according to State policies and standards and said no problems were detected when that happened.

Zhang, the Beijing inspector, also dispelled a rumor that subway operators had been buying light-duty escalators designed for shopping malls to save cost.

"In the Beijing subway system, all the escalators are heavy-duty ones," he said.

The accident this week that killed one and injured 30 happened at 9:36 am on an escalator at Beijing Zoo Station Exit A on Line 4, said Yang Ling, a representative from the line's operator, Beijing MTR Corporation.

On Dec 14, 24 passengers were injured when an escalator, also made by OTIS, reversed direction at a subway station in Shenzhen.

Beijing transport commission on Wednesday ordered the overhaul of all of its 1,331 escalators and elevators at subway stations.

China Daily on Thursday witnessed passengers changing their behavior when using facilities in subway stations.

When riding the ascending escalators, most people put their hands on handrails. Many used to think of the handrails as dirty and did not touch them.

"They kill people. It's not simply that you tumble and get up later," said Xie Wanru, a local logistics manager.

Broadcasts on the city's Line 4 said "passengers with heavy luggage please use the elevators (rather than escalator) for the sake of safety".

Two staff members were seen carefully helping a woman sitting in a wheelchair to use an elevator.

Safe production expert Yu Shengzhang told Beijing Times two major risks exist in the city's escalator operation.

Yu said there is no scanning for faults on escalator parts that bear loads. And he said no one manages the emergency brake button.