6.6 magnitude earthquake strikes near Japan's Ryukyu Islands, USGS says

HIRARA, Japan -- A preliminary-magnitude 6.6 earthquake struck near Japan's Ryukyu Islands on Wednesday, according to the U.S. Geological Survey.

There were no immediate reports of injuries or major damage, and whether the quake would trigger a tsunami warning was unclear.

The earthquake's epicenter was located in the Pacific Ocean, about 115 miles southeast of city of Hirara on Japan's island of Miyako, the USGS said. It occurred at 11:45 p.m. local time and its depth was measured at just over 6 miles.

Great California ShakeOut: LA Metro unveils earthquake early warning system

People in government offices, businesses and schools across Southern California stopped everything for a minute Thursday to "drop, cover and hold on" during a statewide earthquake drill.

DEVELOPING: More details will be added to this report as they become available.