A 6.4-magnitude earthquake followed by strong aftershocks struck Puerto Rico early on Tuesday, killing at least one person, knocking out power and causing significant damage, authorities and media reported.
Governor Wanda Vazquez activated security measures on the island and said all public sector offices except for emergency services would remain closed on Tuesday while emergency plans were implemented.
The island has been rocked by a series of quakes in recent days, including a 5.8-magnitude temblor on Monday that damaged a few homes on the southern coast.
The U.S. territory is still recovering from a pair of devastating 2017 hurricanes that killed about 3,000 people and destroyed significant infrastructure across an island working its way through a bankruptcy process to restructure about $120 billion of debt and pension obligations.
Vazquez, who assumed office in August after Ricardo Rossello stepped down in the face of massive street protests, tweeted pleas for people to remain calm.
"We want everyone to be safe. That is why all work in the public sectors has been suspended today, so that you can be with your family, implementing your emergency plans," Vazquez tweeted.
The Pacific Tsunami Warning Center reported a small tsunami measuring around 20 centimeters (7.9 inches).
The first and biggest quake on Tuesday, of magnitude 6.4, struck at a depth of 10.0 km (six miles) at 4:24 am (0824 GMT) near Ponce on the island's southern coast, the U.S. Geological Survey said.
A 73-year-old died there after a wall fell on him, newspaper El Nuevo Dia reported.
Witnesses on social media described the quake as "super strong" and lasting up to 30 seconds. It was followed by a number of hefty aftershocks including one measuring 5.8.
The impact along the country's southern coast appeared significant.
Puerto Rico Electric Power Authority Chief Executive Jose Ortiz said its Central Costa Sur power plant was damaged, and the utility was checking other substations on the island.
PREPA had cut off power on safety grounds and hoped to reconnect supplies as soon as possible, it said on Twitter.
In the town of Guanica, several buildings collapsed. Further east in Maunabo, video on social media showed people evacuating to higher ground following the tsunami warning.
"Persons along coastal areas near the earthquake should be observant and exercise normal caution, otherwise no action is required," the PTWC said in its warning.
Monday's quake off southern Puerto Rico knocked several houses off their supporting pillars in Guanica and Guayanilla, crushing vehicles beneath them.
That quake also destroyed the Window of the Caribbean, a rock formation on a beach that had been a tourist attraction, but there were no reports of injuries.