CARACAS — Venezuela’s government shut schools and suspended working hours on Friday after the capital Caracas and other major cities awoke without electricity due to a problem that struck the South American country’s main hydroelectric plant on Thursday.

President Nicolas Maduro “has suspended classes and the working day today in order to facilitate the efforts for the recovery of electric service in the country,” wrote Vice President Delcy Rodríguez on her Twitter account.

The government quickly blamed the outage affecting 23 of the country’s 24 states on what it called sabotage of a major hydroelectric dam.

In Caracas, traffic lights went out and the subway system ground to a halt, triggering gridlock in the streets and huge streams of angry people trekking long distances to get home from work.

The blackout in the capital was total and hit at 4:50 p.m. (2050 GMT), just before nightfall. Caracas is one of the world’s most crime-ridden cities so people set out for home early, well before the sun went down.

Commerce was shut down because most transactions are done with debit or credit cards. Hyperinflation has rendered the local currency, the bolivar, almost worthless.

Telephone services and access to the internet were also knocked out. The capital’s international airport was hit, according to social media posts from would-be travelers. A Copa Libertadores football game in the city of Barquisimeto was postponed.

As night set in, the nationwide outage dragged on and some people in Caracas banged pots and pans — a traditional Latin American method of letting off steam.

About seven hours after the mess started, the lights did come back on in some buildings in eastern Caracas.

Venezuelans are wearily accustomed to blackouts. For years they have been common in the west of the oil-rich country, but have eventually spread to Caracas and other areas.

“We are tired. Exhausted,” said Estefania Pacheco, a sales executive forced to walk 12 kilometers (seven miles) from her office in eastern Caracas to her home across town.

“It is so sad every time this happens,” said the mother of two.

Critics blame the government for failing to invest in upkeep of the electrical grid, although the government often blames what it calls sabotage when the lights go out.

This time, Vice President Delcy Rodriguez alleged that “extremist sectors” had waged “a large scale attack.” She insisted power was back on in some eastern states.

The state power company Corpoelec said there has been sabotage at a big hydroelectric plant called Guri in Bolivar state. It gave no details. The facility is one of the biggest in Latin America.

“It’s part of the electric war against the state,” the company said on Twitter.

“We won’t allow it. We’re working to re-establish the service.”

A year ago, Maduro asked the armed forces to provide security to protect the country’s hydroelectric facilities but power outages continue.

Maduro tweeted that the blackout was part of a war directed by what he called US imperialism. It will fail, he added.

“Nothing and no one can defeat the people of Bolivar and Chavez,” Maduro said, referring to the liberation hero Simon Bolivar and Maduro’s predecessor and former boss, the late socialist icon Hugo Chavez.

Maduro is struggling in the face of a challenge by opposition leader Juan Guaido, who has declared himself to be interim president and is now backed by some 50 countries led by the United States.

Guaido says Maduro’s rule is illegitimate, arguing that his re-election win last year was fraudulent, and he wants Maduro to resign from the Miraflores Palace and make way for new elections.

Secretary of State Mike Pompeo said Maduro is wrong to blame the US or any other country for Venezuela’s woes.

“Power shortages and starvation are the result of the Maduro regime’s incompetence,” he tweeted.

Guaido tweeted that Venezuela has plenty of hydroelectric plants and more. “We have water, oil and gas. But unfortunately we have an usurper in Miraflores.”

The blackout also made it virtually impossible for people to shop.

The highest denomination note, 500 bolivars, is worth about 15 US cents, so most transactions are done electronically. Inflation will hit 10 million percent this year, the IMF estimates.

Adriana Bellorin, a lawyer who went out to buy food Thursday evening, said it was futile. “Without electricity I cannot buy anything,” she said. — Agencies