June 16 (UPI) -- Argentina and Uruguay were completely without electricity and other South American countries had a partial blackout after a "massive failure" in an interconnection system, a utility distributor said Sunday.
Much of Paraguay was affected and some residents in Chile and Brazil lost power.
Seven hours after the outage, Edesur posted on Twitter that power had been restored to 80 percent of its 2.5 million customers in Buenes Aires and surrounding communities. The company serves 20 percent of 44.3 million residents in Argentina.
Besides knocking out electricity in homes, businesses and street lights, it affected some water supply and public transportation, the Argentine news site Infobae reported. Flights were taking off and landing because airports were operating on generators.
Voting sites in Argentina's regional elections were disrupted, including some ballots cast in darkness.
"There is a complete blackout in Argentina," said Alejandra Martínez, a spokeswoman for Edesur said in a report by The New York Times. "This is the first time something like this has happened across the entire country."
Edesur posted on its website a "collapse" in its system occurred around 7 a.m. and the cause is under investigation. It was linked to a failure in the transmission of electricity from the Yacyreta hydroelectric dam on the Paraná River.
Three hours later, the company posted on Twitter it had begun generating electricity in the Argentine capital and the surrounding area.
At 11:53 a.m., the utility tweeted power was restored to 450,000 customers, with priority to hospitals and health centers.
"We prioritize the attention of independent users, but due to the gravity of the failure in the electric network of Argentina we recommend attending a nearest hospital or health center if necessary," the utility posted on its website.
Uruguay's energy supplier, UTE, also posted on Twitter that a malfunction in the Argentine network before dawn had left the "entire national territory" without service. A total of 6.8 million live in the nation.
In 2009, a power failure in Brazil involving the world's largest operating hydroelectric plant caused widespread blackouts that affected tens of millions of people.