Tens of millions of people were left without power for hours on Sunday and into Monday after an electricity outage across Jakarta and surrounding areas.

The blackout began at midday Sunday (local time) and lasted well into the night, affecting an area where about 100 million people live.

It hit Jakarta’s new metro train network, which was forced to evacuate after trains ground to a halt. Mobile phone networks were also hit, and traffic lights went out – in a city notorious for its bad traffic.

Generators were used in some offices, malls and apartments.

Indonesia’s state power company PLN blamed technical issues for the failure.

“Hopefully for the Jakarta system, if everything goes to plan and the generating system is reliable, smooth supply should return in approximately three hours,” acting chief executive of PT Perusahaan Listrik Negara (PLN) Sripeni Intan Cahyani said.

Ms Cahyani said customers in West Java and Banten should get power back within four to five hours.

She blamed faulty transmission circuits on the Ungaran to Pemalang power line in Central Java for causing voltage drops that hit power networks in Jakarta as well as West Java and Banten provinces.

“We will investigate to find the root causes and analyse them in detail. We will appoint an independent party to investigate,” said Ms Cahyani, who only started in her job on Friday.

Another PLN official said two out of three circuits had gone down triggering “cascading voltage” that caused outages as the west system collapsed.

Earlier on Sunday, Jakarta’s mass rapid transit system had to evacuate passengers from trains after the power outage put trains out of action.

Jakarta is Indonesia’s centre for government and business and is home to more than 10 million people. About three times that many live in the surrounding towns.

The capital does suffer periodic blackouts, but they are usually short-lived and confined to certain areas.

-with AAP