Power has returned to about 80 percent of Chile after a massive power blackout hit most of the country, Interior Minister Rodrigo Hinzpeter said Sunday night.

He told local radio that power has been fully restored in the regions of Atacama and Maule and were returning to Santiago and the port city of Valparaiso.

Officials were expecting a full recovery to all affected areas in a few hours.

Sources of the Interior Ministry told Xinhua that technicians believed a transformer failure of a main power grid in central Chile was the main cause of the blackout.

Following the sudden loss of power in Santiago, people were seen running out of homes, subway stations and theaters in panic, and many people gathered around street parks. Streets were congested with vehicles as drivers pulled over to see what happened.

The local fire department said there were no reports of casualties related to the blackout yet, but local media said some people might be caught in elevators in high-rises.

The area affected by the power cut includes the southern regions of Maule and Bio Bio, which were hit hardest by the massive Feb. 27 earthquake.

Xinhua reporters in Conception, a city battered by the quake, said the southern city was plunged into complete darkness after the blackout struck.

The sudden loss of traffic lights led to chaos on the busy roads and streets of Conception, which was yet to recover from the devastating quake and ensuing tsunami.

Hinzpeter said the blackout was not directly related to the Feb. 27 earthquake, but investigation would be carried out to see whether there was an indirect cause.