A government source said it was too early to tell whether his death was due to electrocution via faulty machinery or natural causes such as a heart attack.

"An autopsy will be carried out," a police spokeswoman said, adding that an initial investigation found nothing suspicious.

Officers from the Labour Department took statements from Lam's colleagues and inspected the site and machinery, while his family members burned incense and paper offerings.

The house where the worker died was cordoned off and work was suspended on the whole project, which involved demolishing five Hakka-built houses more than 100 years old to make way for six modern homes.

There have been four fatal industrial accidents in the last five weeks.

On Thursday last week, a construction worker was hit by a metal pole at a Ma On Shan site. The 63-year-old was the father of Gavin Kwai Sze-kit, a former League of Social Democrats official who averted an arson attack on an MTR train in 2004. On July 26, a worker, 55, fell from a ladder while cleaning windows at Pamela Youde Nethersole Eastern Hospital in Chai Wan.

The Association for the Rights of Industrial Accident Victims said the number of industrial accidents had risen this year. Since January, it had handled 15 cases of deadly construction accidents.

Its chief executive, Chan Kam-kong, said: "Workers have told us the Labour Department appears to be understaffed [and] on-site inspections took place sometimes [just] once a year."