HAVANA (AP) — Cuban officials said they expect to restart a large thermoelectric plant on Saturday after it shut down earlier in the week, sparking a massive blackout.

Felix Estrada Rodríguez, a top engineer at Cuba’s Electric Union, told state-owned Canal Caribe that the Antonio Guiteras plant should be operating by Saturday afternoon.

Crews have repaired a broken boiler at the plant that caused the outage on Wednesday, leaving millions without power in the island’s western region.

Estrada Rodríguez said it was a slow process that had to be done safely.

“It is a confined space with a high temperature,” he said.

Cuba’s Electric Union said in a statement Saturday that only 1,000 megawatts of power were available, less than half of the island’s current demand. It did not say how many customers remained without power.

The blackout, the second such outage to affect western Cuba in three months, was blamed on a crumbling electric grid and a lack of fuel.

Cuba, which imports most of its oil from Venezuela, recently implemented austere fuel-saving measures after the U.S. attacked the South American country and arrested its leader, leading to a halt in critical oil shipments.

Just weeks after the attack on Venezuela in early January, U.S. President Donald Trump warned that he would impose tariffs on any country that sells or supplies oil to Cuba.