Video shows the 45-metre-long machine quickly changing direction and reversing at speed, causing a human pile-up at the base of the moving staircase at Langham Place in the Mong Kok area of Kowloon.
Screams can be heard as some people tumble down, while others are able to grab the handrail and steady themselves.
“It was fast and people couldn’t respond immediately," Lau Kit-ying told the South China Morning Post. "More than 10 people piled up near the base of the escalator afterwards.”
Another woman told the newspaper that the escalator was travelling at twice the usual speed when it reversed.
Eyewitnesses told local media that 14 women and 3 men were hurt in the accident after losing their balance and rolling down the escalator.
They were treated by rescue workers at the scene.
A Langham Place spokeswoman said the escalator had passed a recent safety inspection. Annual inspections are carried out twice a year, while routine checks are done once every two weeks, she added.
She said Otis Elevator Company (HK) Limited, who are responsible for maintaining all the elevators in the shopping mall, has been asked to investigate the cause of accident.
Langham Place cost around £10 billion to build and is regarded as a flagship project of the country’s urban redevelopment. It comprises 1.8 million square feet in total, including a 665-room five star hotel and an office tower as well as the shopping centre, all held together by a glass atrium with an artificial “digital sky”.
The 15-storey mall attracts more than 200,000 visitors every day and has nearly 200 shops.