Puerto Rico woke up in darkness today following a malfunction in the distribution network that left almost the entire island without electricity.

About 90% of customers were without power as of 9:30 a.m. (3:50 p.m. Greece time), according to the real-time portal of the energy distribution company Luma Energy.

It may take 24 to 48 hours to restore power, “if conditions allow,” Luma stated in an announcement.

“While the cause of the outage is under investigation, preliminary findings point to a failure in an underground line,” Luma added.

Iván Báez, spokesperson for the electricity generation company Genera, described the incident as a “serious event” in an interview with a local radio station.

He noted that the malfunctioning line, reportedly managed by Luma, caused shutdowns at units owned by Genera as well as private power generation companies. Genera’s website reported that two units were back in operation as of 9:30 a.m.

Puerto Rico often experiences power outages due to its deteriorating infrastructure. The island was severely affected by Hurricane Maria, a Category 4 storm, in 2017.