SAN JUAN, Puerto Rico - A 6.0-magnitude earthquake struck near Puerto Rico late Monday, rousing and scaring many from their sleep in the U.S. territory.
The U.S. Geological Survey said the quake struck 49 miles off the island's northwest coast at a shallow depth of 6 miles. Three aftershocks, of magnitude 4.7 and 4.6, hit within less than an hour in the same region at the same depth.
Puerto Rico Gov. Wanda Vázquez Garced said on Twitter that there were no immediate reports of damage. There was no threat of a tsunami, according to the National Weather Service Pacific Tsunami Warning Center.
Kiara Hernández, spokeswoman for the island's Emergency Management Agency, said emergency management officials were already on alert for the approaching Tropical Storm Karen and communicated quickly with mayors and others across the island to check on any damage.
The National Guard also had been activated for the storm, and schools and government offices remained closed.
Karen was expected to bring heavy rainfall, flash floods and possible mudslides on Tuesday to Puerto Rico and the U.S. and British Virgin Islands, according to the National Hurricane Center.
Hernández said crews would be inspecting buildings to ensure their safety.
"We will know this information little by little," she said.
The quake was felt across Puerto Rico and was the strongest to hit the island in recent years. While Puerto Rico experiences very small earthquakes on a daily basis that no one feels, seismologists have said it's rare for bigger ones to strike the island.
Yahaida Zabala, a 46-year-old San Juan resident, was asleep when she felt her building sway Monday around 11:23 p.m.
"I rushed into my son's room," she said. "He was sitting like he was paralyzed."
They ran down the stairs of their building and stood outside with a small group of people awaiting aftershocks.
The last strong quake to shake the island in recent years occurred in January 2014, when a magnitude-6.4 tremor struck after midnight just north of the island's north coast at a depth of 17 miles. Authorities reported broken windows, a busted water line and cracked floors and walls, along with some power outages.
Some 70 aftershocks were reported afterward, with at least three of a magnitude 3.5 or greater.
The most damaging earthquake to hit Puerto Rico in recent history occurred in October 1918, when a magnitude-7.3 quake struck near the island's northwest coast, causing a tsunami and killing 116 people.
This story was reported from Cincinnati. The Associated Press contributed.