A worker died on Wednesday after falling from height at a village house in Tuen Mun.
The victim, 44, was unconscious as he was rushed to hospital.
He was later declared dead.
The Association for the Rights of Industrial Accident Victims said the man was a cleaner and maintenance worker.
The group said he was working on the rooftop of a village house in Tai Lam Chung when tragedy struck.
It urged bosses to provide safety belts for employees working at height and make sure they use them.
The Labour Department said it is investigating the cause of the accident.