A fault in an underground cable was the cause of the blackout that hit 19 blocks in Bukit Panjang on Tuesday night.
The electricity supply disruption occurred at 10.08pm, with power being progressively restored from 10.52pm and fully restored by 11.18pm the same night.
Responding to queries from The Straits Times, Minister for the Environment and Water Resources, Dr Vivian Balakrishnan, said SP Powergrid (SPPG) later informed him that there had been a fault in a 6.6-kilovolt underground cable serving the area. "I have asked for a full investigation of the cause and expect SPPG to take all the necessary repairs without further disruption to our residents," he said.
The affected blocks along Petir Road, Cashew Road and Pending Road were in areas represented by Dr Balakrishnan and Bukit Panjang MP, Dr Teo Ho Pin. The minister said he had been informed almost immediately by affected residents.
Dr Teo and Holland-Bukit Timah MP Liang Eng Hwa were also in the area and in touch with the town council and SPPG.
"Our main priority was safety as the blackout affected traffic lights, lifts and corridors," said Dr Balakrishnan. Town council emergency response teams were deployed in case people had to be rescued.
Some residents told The Straits Times that nearby traffic lights and street lamps were also affected by the blackout, with police officers having to direct traffic instead.
Said Dr Balakrishnan: "I drove to the affected area and made a house-call on a patient with a serious condition that made him dependent on a mechanical ventilator to breathe. The SCDF (Singapore Civil Defence Force) staff and I were able to confirm that he was not affected at all by this incident.
"I am very grateful to SCDF as they had to carry all their equipment up eight flights of stairs. They were professional and cheerful."
For residents, when the blackout happened, most were already at home. The main inconvenience was the lack of fans or air-conditioning to beat the heat, they said.
Said technician Rosman Kamsin, 38: "I woke up because it was very hot. I just had to wait for the power to come back on."
Housewife Loh Kah Hong, 57, also found it too hot. But the duration and the timing meant it was not a big issue, she added: "Luckily it was only an hour. If it had been 11-something, 12-something, then it would be very tough. But we weren't going to sleep yet."
For two of Mrs Sheena Low's three daughters, the blackout did not stop their late-night studying.
"They used the torchlight from their handphones and candlelight to continue," said the 43-year-old business owner. Her older daughters are taking their A-level and N-level exams this year.