An earthquake with a preliminary magnitude of 6.4 rattled Southern California on Thursday and prompted a series of aftershocks that sprawled across the region.

The quake centered near the California town of Ridgecrest, roughly 150 miles northeast of Los Angeles, according to the US Geological Survey. Ridgecrest has a population of roughly 29,000 people.

The earthquake was felt from Las Vegas, Nevada, to the Pacific Coast of California, the Associated Press reported.

The Kern County Fire Department said first responders were working nearly two dozen incidents in Ridgecrest, ranging from medical assistance calls to structure fires.

The Ridgecrest Regional Hospital was also being evacuated, the fire department said.

Experts warned at a press conference that aftershocks will continue after the quake. Seismologist Lucy Jones told reporters that there's a greater than 50 percent chance of having magnitude 5 aftershocks, and even a possibility that the largest quake hasn't yet occurred.

"There is about a 1 in 20 chance that this location will be having an even bigger earthquake in the next few days, that we have not yet seen the biggest earthquake of the sequence," Jones said.

It's the largest quake to strike Southern California since 1999, Jones said.

And though the Ridgecrest area is "sparsely inhabited," there was still a chance for damage.

"This earthquake was large enough where the shaking could have caused damage," seismologist Rob Graves told reporters.

President Donald Trump said in a tweet Thursday afternoon he was "fully briefed" on the quake.

"All seems to be very much under control!" he said.

This is a developing story. Please check back for updates.

This article was originally published by Business Insider.