A rare blackout hit the entire Dominican Republic on Tuesday, snarling traffic and paralyzing businesses in the country of nearly 11 million people.

Officials blamed a failure in the grid's transmission system, although it wasn't immediately clear what caused it.

Generation units in San Pedro de Macorís and the Quisqueya Power Plant shut down, triggering a cascade of failures at other transmission and generation plants, according to the Dominican Electricity Transmission Company, a decentralized state agency.

It wasn't immediately clear how quickly power would be restored.

The blackout disrupted mass transit systems, including aerial cable cars and the metro in the capital, Santo Domingo. Passengers trapped inside the metro and cable cars when the power went out were evacuated, the Agence France-Presse news agency reported. Some people disembarked from the train and began walking through tunnels alongside the railway. Hospitals, banks and other large institutions were relying on generators, but many homes and small businesses were without power.

The situation is made worse because power went out during the afternoon rush hour, according to local newspaper Diario Libre.

"Traffic is already chaos in eastern Santo Domingo," said Tomás Ozuna, 37, as he headed to his night shift as an IT worker. "I don't know how we'll work."

Social media users reported power outages in various parts of the country, although electricity and internet were operational in some places, according to AFP.

Meanwhile, Lissa Fernández, 26, said there was a generator at the bank where she works, but she wasn't sure how she would get home. "The metro isn't running. I have to figure out how to get there," she said.

Leonel Encarnación, who owns a barbershop in Santo Domingo, said his business was full when the blackout hit.

"Ever since the air conditioning shut down, the clients left," he lamented.

Most of the Dominican Republic's energy supply is fueled by oil and its products, followed by coal, natural gas and, to a lesser extent, solar, wind and hydroelectric power, according to the International Energy Agency.

In recent weeks, Dominican citizens have experienced outages lasting up to 10 hours due to what the board of electricity distribution companies said was the result of a lack of maintenance as well as illegal connections, AFP reported.

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