Sri Lanka announced lengthy daily power cuts nationwide as the state-run electricity monopoly struggled to restore supply after the island's worst blackout in 20 years.
The Ceylon Electricity Board said its main Chinese-built coal-fired power plant that supplied more than half the country's electricity was still offline following a massive system breakdown on Sunday.
"We will need a few days more to get this power station online and this means we need to ration electricity across the country on a staggered basis," a board official told AFP.
Several small plants are now supplying power to the whole of the country until the 900-megawatt plant is restarted, but cannot produce enough electricity to go around.
The cuts will occur for seven and a half hours -- five and a half hours during the day and two hours at night -- the official said, without saying how long the rationing would last.
Authorities are probing the cause of an explosion and fire at a main distribution centre outside the capital Colombo on Sunday that caused the entire electricity grid to switch off automatically.
Power and Energy Minister Ranjith Siyambalapitiya has said authorities have not ruled out sabotage.
The country, which suffers sporadic power cuts, was plunged into darkness for at least seven hours on Sunday before electricity was restored.
The former government's power minister criticised the Chinese-built plant in 2014, saying it had broken down more than 35 times in the first three years of operation.
Sunday's was the second major power failure in less than a month, following a three-hour disruption in late February, and the worst since May 1996 when the entire country was without electricity for four days.
The latest outage came as an investigation was under way into last month's embarrassing disruption during a visit by New Zealand Prime Minister John Key, who had described Sri Lanka as a shining light in Asia.