SINGAPORE - Six months after a road viaduct collapsed in Upper Changi Road East, investigations into the accident, which killed one worker and injured 10 others, have not been completed.

Transport Minister Khaw Boon Wan said in a written parliamentary reply on Monday (Jan 8): "Investigations are still ongoing. After investigations are completed, the matter will be referred to the Attorney-General's Chambers for their assessment."

"More information will be provided at the appropriate juncture," he said in response to a request for an update from Workers' Party Non-Constituency MP Dennis Tan Lip Fong.

Last August, Senior Minister of State for Transport Lam Pin Min told the House that investigations into the July 14 tragedy would be wrapped up by October.

It is not known what is causing the delay, or when the probe will now be completed.

Listed home-grown engineering firm OKP Holdings clinched the viaduct project in 2015 for $94.6 million - the lowest bid.

In August, Dr Lam revealed that a price-quality ratio of 70:30 was used to assess bids for the ill-fated viaduct project. In the quality component, the Land Transport Authority assigned 25 per cent to safety.

He noted OKP "actually scored the lowest for quality in the project submission", although it had the highest price-quality score overall.

Post-incident checks revealed cracks at 11 other locations along the failed viaduct. It has also emerged that a consultant from CPG - OKP's sub-contractor - who designed the viaduct was also the supervisor who checked the construction works.

While the practice is not illegal, industry players said it is not ideal.

The viaduct, linking Tampines Expressway to Pan-Island Expressway and Upper Changi Road East, is slated to be completed by the first quarter of 2020.

Work has halted since the collapse, and will not resume until investigations are over.