Hurricane Maria pounded the U.S. Virgin Islands late Tuesday and into Wednesday on its way to Puerto Rico.
The U.S. National Hurricane Center said the outer edge of the storm's eye was lashing the island of St. Croix as Maria carried maximum sustained winds of about 280 kilometers per hour and rains that forecasters say will cause life-threatening flash floods and landslides.
The NHC said the storm is "potentially catastrophic" and is expected to remain a dangerous Category 4 or 5 hurricane as its center goes directly across Puerto Rico by Wednesday night.
Puerto Rico Governor Ricardo Rossello said "major damage is inevitable" in the U.S. territory and that officials had set up 500 shelters.
U.S. President Donald Trump has issued state-of-emergency declarations for Puerto Rico and the U.S. Virgin Islands, and authorized the Department of Homeland Security and the Federal Emergency Management Agency to coordinate all relief efforts.