Prime Minister Ahmet Davutoğlu has said officials are inspecting all possible causes, including a terror attack, for the electricity cut across Turkey, as power blackouts continue in several provinces including Istanbul and Ankara.
Officials told daily Hürriyet that a technical problem in the system of the Turkish Electricity Conduction Company (TEİAŞ), which operates energy transmission lines, led to the massive outage.
At least 44 provinces throughout Turkey are affected by the outage.
Energy Minister Taner Yıldız has said teams are working to determine the cause of the blackout, ruling out claims that the country is suffering an energy shortage.
“I also cannot say whether or not there was a cyber attack,” Yıldız said.
Davutoğlu has said "all possibilities," including a terror attack, are being investigated.
Istanbul Metropolitan Municipality announced in a statement that metro and tram services had been halted due to the blackout.
The Energy Ministry has also released a statement, saying a problem has occured with the main distribution lines and the cut is likely to have originated in the Aegean region.
The blackout is the biggest power outage in Turkey in 15 years, the ministry added.