Cuba remained largely without power on Saturday morning after the island´s grid collapsed the night before, knocking out electricity for 10 million people and raising fresh questions about the viability of its antiquated generating system.

Cuba’s power grid collapsed Friday night, triggering a nationwide power outage and plunging its more than 10 million people into darkness.

An outage at the Diezmero substation on the outskirts of Havana had caused “a significant loss of generation in western Cuba and, with it, the failure of the National Electric System.”