It was the wee hours of the morning and the workers were almost done with casting the deck of a new viaduct using cement.
They were supposed to pour 60 cubic m of cement onto a slab and had just 10 cubic m to go when the beam they were standing on collapsed, sending them falling 4m to the ground.
The incident at 3.30am yesterday at a viaduct in Upper Changi Road East left Chinese national Chen Yinchuan, 31, dead and 10 others injured. The workers were employed by subcontractors of construction firm OKP Contractors. One of the injured workers was from Transit- Mixed Concrete, while the other 10 workers were from Tongda Construction & Engineering.
An employee of Tongda, who declined to be named, told The Straits Times at its Ubi office: "According to my boss, they had almost finished. There was just another 10 cubic m (of cement) to go."
Mr Chen had arrived in Singapore for work in April this year. Records showed that he had been certified "competent" after he was assessed on April 24 for a workers' construction safety orientation course.
The Tongda employee repeatedly asked about the condition of the other workers, most of whom are believed to be in their early 20s.
"Is everyone okay?" the employee asked. "I am concerned about the workers right now because I am quite close with the supervisor who is now in ICU (intensive care unit)."
The injured included site supervisor Gao Liqin from China, whose right hip was impaled by a reinforcement bar.
The Tongda employee said: "I am close to some of the workers, not that I always see them, but I have been working at the company for some years." He said the company boss had called yesterday morning to say the beam had "gone down".
When contacted, the employee's superior said he had "no time to talk" and hung up.
At the accident site, a worker said the injured included a man who broke his leg, and another who was impaled.
The hours following the incident saw grim, frenzied activity in Upper Changi Road East. Police and Singapore Civil Defence Force (SCDF) personnel were seen rushing around at 4.30am, with SCDF's Disaster Assistance and Rescue Team officers present as well. They were conducting a search in the rubble and used search dogs as well.
Most of the workers at the scene had rushed down from their dormitories to check on their friends after learning of the accident.
The 10 injured workers were taken to Changi General Hospital. As of 7am, search and rescue operations had been completed.
Residents at a nearby block reported hearing a loud noise, but many were unaware of the extent of the accident. "There was a notice to say they would be working in the night for two days this month, so I didn't think too much about it," said Ms Koh Geok Lan, 60, who lives across the accident site, at Block 346, Tampines Street 33.
But in the morning, she realised the structure connecting the uncompleted bridge was gone. "The red structure (connecting the uncompleted parts of the bridge) had been up for a while, and I have seen many men working on top of it every day," said Ms Koh.
Ms Shriya Sriram, 20, a university student who lives in the same block, said: "It was a very loud sound - there was a screech. It was very metallic-sounding, but I assumed that they were moving something and it dropped."