Snapped wires may have led to Monday's National Art Gallery crane accident which killed two workers, said Acting Manpower Minister Tan Chuan-Jin.
Calling it a "serious incident" after a visit to the construction site along St Andrew's Road on Tuesday, he added that it was still too early to say what actually happened.
It appears that there had been "nothing unusual" with the operation of the crane, and the weight of the excavator it had been lifting was well within limits.
"So the next step really is to determine what exactly happened - is it technical in nature, is it a systemic problem - so that lessons can be learnt, rectifications can be made," explained Mr Tan. "Not just here, but whether there are lessons for the industry as well."
The Manpower Ministry has ordered work at the site to be stopped for its investigations.
Project director Hideki Izumi, who works for the main contractor Takenaka-Singapore Piling Joint Venture, said the worksite's tower cranes, which were leased from Waheguru, were inspected monthly even though the industry norm is once every three months.
The crane, the boom of which collapsed at the Coleman Street site on Monday morning, was last inspected on Sept 19.
Its concrete counterweights fell too, crashing through scaffolding and killing a worker. Another died after being hit by the crane's hook assembly.
The bodies of Thai national Somkhot Chanyut, 50, who worked for Yong Nam Engineering, and Takenaka Corporation employee Ronju Ahmed, a 30-year-old from Bangladesh, was flown back on Wednesday.