A blackout hit much of Venezuela yesterday, including the capital Caracas.
President Nicolas Maduro said his political opponents may have been behind the power cut.
The blackout struck a dozen of the South American country's 24 states and caused traffic chaos in parts of the capital and other cities.
A senior energy ministry official said a fault occurred in one of the national grid's major transmission lines, which caused power cuts in the west and centre of the country.
"It's going to take several hours to restart the generation plants so we can restore national service," Franco Silva, vice minister of electricity development, told state television.
President Maduro said he had ordered the armed forces to help ensure security while power was being restored.
"At this moment, everything seems to indicate that the far-right has resumed its plan for an electrical strike against the country," Mr Maduro said on Twitter.
The OPEC nation's oil refineries, which are powered by separate generator plants, were not affected.
