GUAYANILLA, Puerto Rico (CNN/ AP) — A 6.4-magnitude earthquake struck Puerto Rico before dawn on Tuesday, killing one man, injuring at least eight other people and collapsing buildings in the southern part of the island.

The quake was followed by a series of strong aftershocks, part of a 10-day series of temblors spawned by the grinding of tectonic plates along three faults beneath southern Puerto Rico. Seismologists say it’s impossible to predict when the quakes will stop or whether they will get stronger.

The 6.4-magnitude quake cut power to the island as power plants shut down to protect themselves. Authorities said two plants suffered light damage and they expected power to be restored later Tuesday. Puerto Rico’s main airport was operating normally, using generator power.

Puerto Rico’s governor, Wanda Vásquez, declared a state of emergency and activated the territory’s National Guard. She said some 300,000 households remained without running water by late Tuesday afternoon, and several hundred people were in shelters in affected municipalities. She said she had not spoken to President Donald Trump by late morning.

The U.S. Geological Survey said the quake hit at 4:24 a.m. just south of the island at a shallow depth of six miles (10 kilometers). It initially gave the magnitude as 6.6 but later adjusted it. At 7:18 a.m., a magnitude-6.0 aftershock hit the same area. People reported strong shaking and staff at a local radio station said live on air that they were leaving their building.

This comes following the destruction of Puerto Rico’s famous landmark and cherished natural wonder Punta Ventana collapsed following a strong earthquake Monday after a 5.8 magnitude quake that collapsed five homes in Guánica and heavily damaged dozens of others.

The UPRM Meteorological Laboratory shared a photo on Twitter of Punta Ventana before and after the earthquake, showing where the soaring arch once stood before its tragic collapse.

“The natural window disappears in Punta Ventana, Guayanilla,” UPRM said.

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. Seismologists say that shallow quakes were occurring along three faults in Puerto Rico’s southwest region: Lajas Valley, Montalva Point and the Guayanilla Canyon, as the North American plate and the Caribbean plate squeeze Puerto Rico.