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A 5.8 magnitude earthquake shook the entire island of Puerto Rico on Monday morning, the strongest in a flurry of quakes to strike the U.S. territory in recent days.

The relatively shallow, 6-mile-deep quake struck at 6:32 a.m. just south of the island, where it was felt most strongly, according to the U.S. Geological Survey, or USGS. Several smaller temblors followed, including a 4.9 magnitude quake that frightened residents all over again just before 11 a.m., according to the USGS.

There was no tsunami threat, and no deaths or injuries had been reported, according to officials.

People were forced outside their homes, afraid to go back inside, as preparations and celebrations for Three Kings Day should have been underway. And thousands of residents lost power after the quake affected some electrical substations in the area.

"My entire family woke up screaming," Dr. Sindia Alvarado, who lives in the southern coastal town of Peñuelas, east of Guayanilla, told The Associated Press. "I thought the house was going to crack in half."

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The southwest coastal town of Guánica opened a shelter after several families lost their homes. At least five residences collapsed in the town, according to reports in El Nuevo Día, the island's largest newspaper.

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Gov. Wanda Vázquez Garced urged people to stay composed as residents in the south posted pictures of damaged houses and of rocks and boulders blocking roads.

"Citizens must remain calm and have their action plans prepared to protect themselves," Garced wrote on Twitter.

She said that she was in touch with the mayors of Guayanilla and Guánica and that bridges and other structures that were inspected following quakes and tremors of the past couple of weeks would be reviewed again.

Sen. Marco Rubio, R-Fla., tweeted that his office was in contact with authorities in Puerto Rico and would help to provide any federal aid that is needed.

One of the island's most iconic landmarks, the Guánica lighthouse, built by the Spanish in 1892, suffered damage after the earthquake. Although the lighthouse's tower survived, one of its front walls collapsed.

In Guayanilla, a rock formation popular with residents and tourists alike known as Playa Ventana — which means "Window Beach," because the rock formed what looked like a window — was gone; the top broke off during Monday's earthquake.

[GUAYANILLA] Desaparece la ventana natural en Punta Ventana, Guayanilla. pic.twitter.com/IN0LI7XuKK — UPRM Meteorological Laboratory (@UPRMetLab) January 6, 2020

"Playa Ventana collapsed. Today our icon remains in our memory," Guayanilla's press officer, Glidden López, wrote on his Facebook page on Monday. On Friday, López had posted a picture showing that a bottom chunk of the rock had detached during the previous week's tremors.

"This is hell," said Alberto Rodríguez, 43, whose home collapsed on its side. "We haven't slept. ... You can't remain calm here. Guánica is no longer a safe place."

The foundation of Silvestre Alicea's home fell on top of his prized blue 1977 Toyota Corolla. He said he jumped from his balcony as the house crumbled.

Jose Francisco Benitez, a lawyer, was at a hotel in Guánica when the quake hit. Panicked guests who tried to flee in their cars came to realize that large boulders were obstructing the only highway leading north to San Juan, he said.

"I have never felt anything like this," Benitez said. "It was like a giant grabbed our room and shook it."

"There was a state of panic," he said, adding that people flooded out of their hotel rooms in their underwear.

The head of Puerto Rico's Emergency Management Agency, Carlos Acevedo, said Monday's quake was the strongest since the first in a series jolted the island Dec. 28. That 4.7 magnitude quake was followed by a 5.1 magnitude quake that also hit near Puerto Rico's south coast, as well as another 4.2 magnitude quake on Dec. 31. Since Dec. 28, more than 1,100 earthquakes have been recorded in the region, most of which have not been felt.

USGS geophysicist Amy Vaughn said that the island is in a seismically active area but that a 5.7 magnitude quake is "a larger event for the region."