Hong Kong police confirmed to the BBC that at least eight people are injured and have been sent to hospital.
They said the fire broke out in the machine room, which eventually led to the scaffolding catching fire. The building is currently under renovation.
No fatalities have been reported and rescue operations are still underway.
The eight who are injured are aged between 31 to 72.
A total of 150 people have been evacuated so far, according to authorities.
All the shops had been vacated during the renovation works, leaving only several levels of the building in operation - mostly restaurants and offices, according to the South China Morning Post.
The fire has been classed as a level three incident, with five being the most severe.
The blaze at the 38-storey World Trade Centre on Gloucester Road was first reported at lunchtime.