Commuters riding the Mid-Levels escalator were alarmed when it jolted to a stop with a loud bang, disrupting the service for more than two hours.
No one was hurt in the incident, in which two comb plates fitted where the steps overlap came loose, triggering an automatic stoppage.
Merian Lee Man had just stepped off the down escalator from Robinson Road to Mosque Street on Wednesday morning when she heard 'a loud bang, and a lot of clanging'.
'When I looked back, the [comb plate device] was sticking up,' she said, adding that the escalator came to a sudden stop and a man near the plate had to pick his way down.
The escalator had been repaired by the time she went home that night. 'It wasn't anything big, but my heart was pounding after realising how close to that thing I was,' she said.
The Electrical and Mechanical Services Department said there was a breakdown at 7.25am on Wednesday when 'two combs were detached from their original position and the safety device was activated, causing stoppage of the escalator'.
Staff arrived by 7.40am and the service had resumed by 10.05am.
The department started to implement a performance rating scheme for escalators in June, after a similar scheme for lifts was launched in 2009.
While it is not a requirement under the Lifts and Escalators Safety Ordinance, the government has said it hopes the scheme can reflect 'maintenance and safety performance of registered escalator contractors' and help management agents choose suitable contractors.
Points are deducted from a full mark of 100 if escalators do not comply with safety standards and maintenance performance. In the first three months of the scheme, 12 out of the 15 rated contractors scored full marks, while the lowest score was 85.
A child was killed and 30 others were injured in July when an escalator in Beijing suddenly reversed. It emerged that lack of regulation had allowed faulty models to be installed.