Cuba reconnected its national electrical grid and restored power to the majority of the capital Havana by late on Sunday, energy officials said, nearly two days after an island-wide outage knocked out power to 10 million people.

Cuba restored power to most of Havana after a nationwide outage affected 10 million people. The grid collapse was triggered by a shorted transmission line. Oil-fired plants are back online, yet Cuba faces ongoing energy issues due to outdated infrastructure and geopolitical tensions.

Cuba has struggled with blackouts in recent months, including a nationwide one in December. Friday’s power failure was the fourth widespread one in five months. Government officials blame U.S. economic sanctions for the ongoing crisis, while others point to aging infrastructure, fuel shortages and the island’s susceptibility to hurricanes.