Jakarta. Indonesia is investigating the cause of a major power outage that disrupted electricity supplies across several provinces on Sumatra island, with authorities pointing to extreme weather as the likely trigger behind the blackout.

Chief Infrastructure and Regional Development Minister Agus Harimurti Yudhoyono said the government was closely monitoring the situation and working to determine the root cause of the disruption, which struck parts of Jambi, West Sumatra, Riau, North Sumatra and Aceh on Friday night.

“We must ensure that the most basic public services, including electricity, remain available,” Yudhoyono, widely known as AHY, told reporters in Jakarta on Monday. “The incident is still being investigated to determine the main cause.”

The blackout disrupted electricity supplies across large parts of Sumatra, one of Indonesia’s most populous islands and a major hub for plantations, mining and industrial activities. 

State utility PLN said the blackout began on Friday evening after a disturbance hit a 275-kilovolt extra-high-voltage transmission line linking Muara Bungo and Sungai Rumbai in Jambi province, triggering a cascading failure across Sumatra’s interconnected power grid.

The outage affected around 13.1 million customers across several provinces in Sumatra, including Jambi, West Sumatra, Riau, North Sumatra and Aceh. PLN said it had restored electricity to more than 8.3 million customers by Saturday morning as crews worked to stabilize the system.

PLN President Director Darmawan Prasodjo said the company deployed all available personnel to accelerate restoration efforts.

“Thanks to the tireless work of personnel on the ground and support from the Energy Ministry and regional authorities, Sumatra’s electricity system has now returned to normal,” Darmawan said in a statement on Sunday.

Indonesia’s National Police have also launched an investigation into the blackout. A team from the Criminal Investigation Agency’s special crimes unit was dispatched to inspect a damaged extra-high-voltage transmission line in Tempino village, Muaro Jambi district.

Brigadier General Irhamni, director of special crimes at the National Police’s Criminal Investigation Agency, said investigators, accompanied by forensic experts and PLN officials, had collected damaged conductor cables for laboratory examination.

“So far, we have not found indications of deliberate human involvement in the damaged conductor,” Irhamni said.