Cuba closed schools and halted non-essential work on Friday after a major power plant outage heightened the nation’s chronic energy shortage, prompting widespread blackouts to sweep the island.

Official government reports say six of Cuba’s 15 oil-burning power plants are still operating, but critical fuel shortages have rendered backup diesel generators unable to prop up the collapsing grid. The deteriorating crisis has caused the worst blackouts in over a year, when widespread grid collapses blacked out the entire nation and triggered isolated protests and unrest.

The island’s old power grid has groaned under the weight of decreasing oil imports from Venezuela, Russia, and Mexico. In a move to alleviate the pressure, officials declared non-essential work and schooling suspended, while keeping basic services going.

Even in Havana usually spared the worst of blackouts the inhabitants reported between six and ten hours of outage during the course of the week. In remote towns and cities, outages lasted as much as 20 hours a day. The protracted blackouts have exacerbated people’s ire, piling on to an already desperate scenario underpinned by shortages of fuel, medicine, and food. Since the start of the COVID-19 outbreak, deteriorating conditions have persuaded over a million Cubans to emigrate out of the island in search of a better future.

Cuban officials have attributed the crisis to the longstanding US trade embargo and severe sanctions during the Trump era, which have increasingly limited the ability to get fuel and required grid upkeep supplies. Last month, President Donald Trump revived restrictions that were temporarily rolled back by his predecessor, Joe Biden.

Authorities have promised residents that electricity output is likely to increase slightly this weekend as more fuel supplies are made available. Nevertheless, fears persist regarding the long-term viability of Cuba’s ailing energy industry.