GOVERNMENT factory inspectors today will check every work site using passenger hoists similar to the one which plunged 17 floors in Quarry Bay yesterday, killing 12 workers. It is the biggest toll from an accident on a Hongkong construction site. The worst industrial disaster occurred in October 1986, when a fireball swept through a fur factory at Kwai Chung, after which 14 workers died of their burns. Labour unionists inspecting the Java Road site yesterday called for licensing of hoist operators to prevent further tragedy. Initial investigations by the Labour Department pointed to overloading as the cause of the accident at the new Towngas operations centre. A sign had been attached to the lift after a breakdown yesterday limiting the load to 1,000 kilograms or eight occupants. There are two freight elevators and only one passenger lift, utilising the system in which a cog, driven by an electric motor, engages a tooth rail, virtually climbing the building. But yesterday, 14 men - including the operator - rode the passenger lift to the 20th floor, where two got off. They reported hearing a loud crack just before the cage began plummeting back to the third floor podium. Firemen who arrived at the partly-completed building said most of the victims, the youngest a 16-year-old on a school holiday job, were unconscious. North Point station officer Tong Kwai-lam said: ''There were three layers of humans who were mostly unconscious. Their hands and legs were entangled. ''I heard some people on top moaning and shouting for help but the ones at the bottom looked to be dead already. ''Some of their hands and legs were trapped between the bottom of the crushed cage and the third floor podium.'' It took 15 minutes, using a set of the most sophisticated tools which can cut, pull and jack up wreckage, to free everyone. The equipment, known as Holmatro, was delivered to all fire stations only two days ago. Acting Chief Factory Inspector Kan Hon-sang said a four-man investigation team had been set up and they would be assisted by engineers of the Electrical and Mechanical Services Department. ''We will look at three aspects of the incident which include overloading, periodic inspection and safety devices of the lift concerned. ''We have not ruled out overloading as the cause of the tragedy as it was designed to carry eight people, including the lift operator. ''We were told there were at least 12 people in the lift when it crashed on to the ground,'' he said. Mr Kan said nine teams of 31 factory inspectors and four officers from the site safety task force will today fan out and check multi-storey structures throughout Hongkong. ''We have given the emergency inspection a top priority now that so many workers have died. ''We'll immediately prosecute contractors or site controllers if we find that safety regulations have been ignored,'' he said. The fatal crash occurred at 4.20 pm when a group of workmen, mostly electricians and lift workers, returned to the 25-storey building after a 45-minute tea break. The injured workers were taken to the open ground a few metres from the wrecked hoist where they were given emergency first aid and then loaded on to a fleet of ambulances. A mobile medical treatment centre swung into action at the scene with doctors standing by. The last time the mobile emergency clinic was used was the Lan Kwai Fong disaster on New Year's Eve. Seven workers were certified dead on arrival at the Tang Shiu Kin Hospital in Wan Chai. Five other people were transferred to the Queen Mary Hospital in Pokfulam where they died later. Police divisional commander in North Point, Superintendent Yan Fook-mau, said more than 10 officers of the Eastern district crime squad had been assigned to investigate the fall. ''We want a team of professional police investigators to do a thorough investigation in the light of huge public interest in the case,'' he said. The assistant district commander (crime), Detective Superintendent Don Logan, said an inter-departmental group would also assess the accident. The group compromises Labour, Electrical and Mechanical Services and Fire Services departments, the Government Chemist and police. Overloading was certainly a problem but the team had yet to establish whether there was any fault with other parts like the braking system, Mr Logan said. ''We will meet the management of the building to get their side of the story,'' he said. Four officials of the Electrical and Mechanical Services Department arrived at the scene at 8 pm. Mr Kan said they were told the hoist had been checked and tested ''fairly recently'' by the main contractor, Aoki Corporation from Japan. ''The hoist in question was supposed to have a safety arresting device which can brake on the tooth rail when it slides down. But apparently, this was not working at that time. ''We have to find all the parts of the hoist before reaching a conclusion,'' he said. Under existing labour regulations, legal liability to ensure a safe working environment and safety of workers rests with employers. Employers found to have violated construction site safety rules are liable to a maximum fine of $30,000. They may also face an additional fine of $30,000 and six months' jail under the general duties provisions. The chairman of the Hongkong Construction Industry Employees General Union, Poon To-chuen, said legislation was needed to license hoist operators. He said it was widely known that the Labour Department's factory inspectorate was understaffed and that it was impossible for officers to check safety of more than 1,000 building sites in Hongkong. But Mr Kan said insufficient factory inspectors was an ''old problem'' and it was a question of re-deployment of manpower resources. The workers' union has set up a hotline on 388 6887 to receive phone calls from the families of the victims asking for assistance with employee compensation and burial expenses. District Officer for Eastern, Steve Barclay, said his office was ready to offer help to the victims' families. Three members of the pro-China Democratic Alliance for the Betterment of Hongkong (DAB), led by the chairman Tsang Yok-sing, arrived at the scene at 6.20 pm. ''It is regret that such a very serious incident has occurred and I hope there will be an intensive investigation with the hope that it will not happen again. ''I hope the real cause of the tragedy can be found out soon as we want to know whether it was caused by mechanical fault or lack of safety devices,'' he said.