Two of Puerto Rico’s leading power plants shut down which resulted in a major blackout, according to the Associated Press. The outage hit the U.S. territory’s capital of San Juan and its neighboring areas including Caguas, Bayamon, and Carolina. It’s unclear how many people have been affected by the blackout, but more than 970,000 live in the combined areas.

Officials are working to repair the problem and announced that power has already been restored to Puerto Rico’s main airport and some hospitals. It’s also unclear what caused the shutdown, but Puerto Rico’s Electric Power Authority has been tweeting updates as workers try to find the affected line and repair it. This blackout follows another outage that occurred three weeks ago when a fire erupted at an electrical substation, cutting two power plants offline and leaving many without power for two days. Officials are still investigating the cause of the fire.

These outages have become a new normal in the aftermath of Hurricane Maria, which devastated the island and killed two-thirds of its power-sources in September. More than 15 percent of people on the island are still without power five months following the natural disaster. According to the US Department of Energy, the Puerto Rico Electric Power Authority reported that “84.6% of normal peak load and 85.64% of customers (1,261,513) have been restored and all 78 municipalities are at least partially energized.” Officials announced that they expect power to be restored to the island entirely in May.