A 6.5-magnitude earthquake struck Puerto Rico before dawn on Tuesday, the largest in a series of quakes that have struck the U.S. territory in recent days and caused heavy damage in some areas.
A tsunami alert was initially issued for Puerto Rico and the U.S. Virgin Islands, but later canceled.
The Electric Power Authority reported an island-wide power outage.
The U.S. Geological Survey said the quake hit at 4:24 a.m. just south of the island at a shallow depth of 6 miles. USGS initially gave the magnitude as 6.6, but later adjusted it.
Albert Rodriguez, who is from the southwest town of Guanica, said the tsunami sirens went off before officials canceled the alert. He said there is widespread damage in his neighborhood.
"The road is cracked in the middle and it lifted up," he said.
Victor Huerfano, director of Puerto Rico's Seismic Network, told The Associated Press that he does not have immediate reports of damage or injuries because communications are down for much of the island. He said officials in the large southern coastal city of Ponce told him there was widespread damage.
"We expect that this will be the largest quake for now," he said. "The aftershocks will continue for some time."
A 5.8-magnitude quake that struck early Monday morning collapsed five homes in the southwest coastal town of Guanica and heavily damaged dozens of others. It also caused small landslides and power outages. The quake was followed by a string of smaller temblors.
The shake collapsed a coastal rock formation that had formed a sort of rounded window, Punta Ventana, that was a popular tourist draw in the southwest town of Guayanilla.
Residents in the south of the island have been terrified to go into their homes for fear that another quake will bring buildings down.
The flurry of quakes in Puerto Rico's southern region began the night of Dec. 28. Victor Huerfano, director of Puerto Rico's Seismic Network, told the AP that shallow quakes were occurring along three faults in Puerto Rico's southwest region: Lajas Valley, Montalva Point and the Guayanilla Canyon.
He said the quakes overall come as the North American plate and the Caribbean plate squeeze Puerto Rico.
One of the largest and most damaging earthquakes to hit Puerto Rico occurred in October 1918, when a magnitude 7.3 quake struck near the island's northwest coast, unleashing a tsunami and killing 116 people.