It was a blowtorch that heated materials to a searing 800 deg C - twice as hot as it needed to be.
And in the end, it sparked a slow-burning fire that was undetected as a result of further fire safety lapses and human error.
That was the most likely cause of the blaze in the SingTel Internet-exchange room in October which resulted in a days-long stoppage of its services to many parts of Singapore, SingTel's board committee of inquiry concluded on Monday evening.
Comprising three independent members of the company's board, the committee also sharply criticised the telco's "outdated" cable maintenance system, which uses lead sealant to protect the exit points for cables.
This sealant needs to be heated and shrunk each time the cables need to be maintained.
On Oct 9, the SingTel employee who needed to heat a seal in SingTel's underground cable chamber at its Bukit Panjang exchange for cable diversion works borrowed a blowtorch from a contractor who was with him.
That torch was twice as hot as it needed to be, and it caused the sealant and plastic sheaths on the cables to overheat and smoulder, eventually catching fire.
All this went undetected because the employee - a veteran who had been with SingTel for 30 years - neglected to turn the smoke detectors back on when he went for lunch.