An ancient Puerto Rico rock formation that adorned the background of countless vacation photos, Instagram posts and selfies tumbled into the ocean off the U.S. territory’s southwestern coast on Monday after an unusually strong earthquake shook the island and damaged more than a dozen homes.

The 5.8-magnitude earthquake rocked the coastal municipality of Guayanilla about 6:35 a.m., sending families racing out of their homes as the structures collapsed beneath them. At least one beachside residence was destroyed. Residents have experienced more than a half-dozen strong aftershocks and expect more in the coming days. So far, no injuries have been reported as a result of the tremors and the resulting damage, local authorities said.

Punta Ventana, or Window Point, rewarded tourists to Puerto Rico’s southern coast with a stunning frame for ocean views, with its rocky sea cliff and a hollowed-out “eye” carved by the cerulean blue waters of the Caribbean over millennia. The natural wonder has been a source of pride for residents of Guayanilla, whose mayor adopted the landmark as part of a new logo and slogan: “La Nueva Ventana al Caribe: The New Window to the Caribbean.”

“We’ve lost an important symbol of our town and our natural heritage,” said Guayanilla Mayor Nelson Torres Yordán. “Playa Ventana is iconic to this region and a priceless beautiful resource for a community that has suffered greatly in recent years.”

Town officials said they had been monitoring the rock formation during two weeks of seismic activity that triggered hundreds of small temblors on the island beginning in late December. The shaking loosened gravel and rock that formed the “window’s” top curve, which people used to climb to gain a view from atop the narrow rock bridge.

The sequence of shallow-depth earthquakes originated offshore, but they could be felt across the main island. The intensity of the tremors has ratcheted up in recent months but caused little more than heart palpitations across the island.

The U.S. Geological Survey logged a 6.0-magnitude earthquake in September just off the island’s northwestern coast — a potency not felt since 2014. The last time an earthquake caused any notable damage was in 2010, according to USGS records.

“This is not normal,” said Daniel Hernández, a spokesman for the municipal government. “It’s too many one after the other. Tremors happen sporadically, but nothing like this.”

Each vibration dislodged huge chunks of rock and destabilized the cliff. Town officials feared the worst. For years, the city had been trying to negotiate safe public access to the rock formation because the road to the cliff runs through private farmland. The municipality sponsors excursions to the Ventana that also take tourists to its glimmering beach, Playa Tamarindo, and hiking into the adjacent state forest.

As each tremor grew in intensity, rattled residents grew terrified that a tsunami could bury the small seaside city of about 18,000 people. Authorities said there was no tsunami risk as a result of the earthquake; the last tsunami in Puerto Rico was in 1918.

Residents packed a town hall this week, expressing fears that the power grid — still fragile after Hurricane Maria’s devastation in 2017 — could fail again and that water service could remain interminably interrupted for many barrios, the mayor said.

“We are not okay,” said Torres Yordán, who is asking residents to refresh their emergency plans and identify rendezvous points for family. “We’ve been told that the earthquakes will continue for at least several more days.”

Four hours after the early morning quake triggered Punta Ventana’s collapse, there was a 5.1-magnitude aftershock.

“We tried to get out as quickly as possible, but the shaking was so strong that we could barely walk,” one mother told WAPA Television just before the ground began to quake, provoking screams from reporter Maricarmen Ortiz: “It’s shaking! It’s shaking!”

Local officials are still assessing the damage but so far, one home was destroyed, six suffered severe structural damage and eight others experienced minor damage. At least one road had to be closed due to quake damage. The city used a local school to open a shelter and one displaced family obtained an emergency housing voucher.

Puerto Rico Gov. Wanda Vázquez Garced visited the city Monday evening, but local authorities do not expect the bankrupt central government to be much help. Painful memories haunt Guayanilla officials who have asked the state to provide psychological counseling for residents who are still traumatized by Hurricane Maria and its aftermath.

Guayanilla is one of dozens of local municipalities struggling to recover structurally and economically from the Category 4 hurricane that devastated Puerto Rico. Pounding rain in the central mountains caused flash flooding that bloated rivers downstream and inundated the urban center of the municipality. Hernández estimated there are about 50 families in the municipality that still live under blue tarps because of damage from Maria.

The mayor said he had hoped the area’s rebranding campaign would generate more badly needed tourism dollars for the far-flung southwestern town.

“We have no idea how losing the Ventana will impact us here,” Torres Yordán said. “We could try to rebuild it, but where’s the money for that?”