PNG Power says a riot"was taking place near the station, involving police and local people.
"Electricity supply will not be restored until the situation returns to normal and PNG Power is sure that its property and staff are safe," PNG Power said.
Alotau is the capital of Milne Bay Province.
It is believed that locals were protesting the actions of police officers after one of their vehicles veered off-road at Kwaini and knocked down five people, resulting in three deaths on Monday evening.
Banks, schools and businesses have closed their doors because of security fears.
