Most of Puerto Rico was without power this morning after Hurricane Fiona hit the island with 80 mile per hour winds on Sunday and damaged transmission lines, according to Luma Energy, which operates the island’s power grid.

“The electric system has experienced several transmission line outages which have contributed to an island-wide power outage,” according to a message on the utility’s web site. “Given the size and scope of the outage, as well as ongoing impacts of Hurricane Fiona, full power restoration could take days.”

In a Sunday statement, the utility said it had mobilized almost 2,000 field employees and contractors and “positioned resources around the island to support the safe restoration of power when and where possible.” It had also re-energized some circuits and was restarting generation.

According to PowerOutage.us, 1.32 million of Luma’s roughly 1.47 million customers were without power as of about 9 a.m. EDT on Monday.

“Our @ENERGY Response Organization is activated, and responders are deployed to Puerto Rico and the U.S. Virgin Islands,” Department of Energy Secretary Jennifer Granholm tweeted on Sunday. The agency is working alongside the Federal Emergency Management Agency and “will assist with restoration efforts as it becomes safe to do so,” she said.

In 2017, Hurricane Maria destroyed the island’s electric system, and efforts to rebuild and modernize the grid are ongoing. Luma Energy began operating Puerto Rico’s electric grid last year, managing the system through a public-private partnership while the Puerto Rico Electric Power Authority continues to own the island’s grid assets.