The woman had been taken to hospital unconscious after being freed from the debris.
Dramatic footage posted online showed a huge wall of scaffolding and netting that had covered a building on Broadwood Road collapse into the street shortly after 10am.
The Fire Services Department said it deployed around 100 firefighters and ambulancemen to the scene, and it took them more than an hour to search the debris.
A male worker was rescued. He was not injured.
The scaffolding came down on two cars, but the drivers managed to escape on their own before firefighters arrived. One driver was slightly injured and was taken to hospital.
The Labour Department said it immediately sent staff to the scene and it was investigating the cause of the collapse.
At the time of the incident, the number three typhoon signal was in effect.
The observatory also issued the Black Rainstorm Warning at 11.45am.
Last updated: 2021-10-08 HKT 18:24