A 6.3-magnitude earthquake has been recorded off the north coast of Puerto Rico.
The United States Geological Survey said the tremor struck north of the province of Isabela.
There were no immediate reports of casualties or damage from the earthquake, which the agency said hit at a depth of 10 km (6 miles) about 80 km (50 miles) from Isabela.
The National Weather Service San Juan tweeted: "An earthquake with a preliminary magnitude of 6.3 occurred 44 miles north of Puerto Rico at 11.24pm Atlantic Standard Time.
"No tsunami threat exists for Puerto Rico and the United States Virgin Islands."
The earthquake came as Tropical Storm Karen moved closer to Puerto Rico, albeit in a weakened state.
Karen, with sustained top winds of 40mph is expected to pass near or over Puerto Rico and the Virgin Islands this morning, the US National Hurricane Center in Miami reported.
Tropical storm warnings remained in effect for Puerto Rico, as well as the adjacent US and British Virgin Islands for the next 24 hours.
Parts of Puerto Rico could receive up to 8 inches of rain from Karen, enough to possibly trigger flash floods and mudslides.
Puerto Rico, beset with financial woes and political turmoil, was spared a potential new disaster last month when Hurricane Dorian skirted past the island before laying waste to the northern Bahamas.
Two years ago, Puerto Rico was still recovering from Hurricane Irma when it took a direct hit from Hurricane Maria, which obliterated large swaths of the territory and left much of the island without electricity for months.
Around 3,000 people perished in that storm, the deadliest in the island's history.
