SYDNEY (Sept 29): Power was restored to the state of South Australia on Wednesday, after storms a day earlier caused an unprecedented statewide blackout which disrupted operations at mining majors like BHP Billiton, closed ports and halted public transport.

The blackout of the country's fifth most populous state, with 1.7 million people, prompted calls on Thursday for an inquiry into the power sector and questions over whether the state's reliance on renewable energy exacerbated the situation.

Authorities said power had been restored to 90% of the state by Thursday morning, but further disruption was possible with gale force winds and heavy rain forecast.

"Let's focus now and take this incident as a real wake-up call...lower emissions is very important but it must be consistent with energy security," said Australian Prime Minister Malcolm Turnbull.

Coal-fired power plants dominate the country's power sector resulting in Australia being one of the world's biggest carbon emitters on a per capita basis. Renewable energy has struggled to increase its footprint in recent years due to scepticism over climate change amongst some the country's leading politicians.

South Australia, a major wine producer and traditional manufacturng hub, is one of the few state's with a heavy reliance on renewable energy. Wind power provides roughly 40 percent of the state's electricity supply.

"Questions have to be asked: Is their over-reliance on renewable energy exacerbating their problems and the capacity to have a secure power supply," Australia's Deputy Prime Minister Barnaby Joyce, a climate change sceptic, told Australian Broadcasting Corp radio on Thursday.

The blackout happened after strong winds destroyed major powerlines north of the state capital Adelaide and lightning struck a power plant, causing a surge across the grid. The network and link to neighbouring Victoria state shut down to prevent damage to infrastructure, causing a state-wide outage.

Power supply was disrupted to BHP Billiton's huge Olympic Dam copper-uranium mine, halting production until back power could be diverted to maintain "essential infrastructure". . Oz Minerals Ltd suspended copper and gold production at its Prominent Hill mine north of Adelaide, which was not damaged.

South Australian independent Senator Nick Xenophon said an inquiry should examine whether the power failure could have been avoided, if more gas-burning power plants had been on standby.

Australia wants to double its large-scale renewable energy generation to 33,000 gigawatt hours by 2020, which means solar, wind and hydro-electricity would have to make up nearly a quarter of power generation by then.