The earthquake struck Chishang Township, a rural area in southeastern Taiwan, with a focal depth of 10 kilometers.
The Japan Meteorological Agency issued a tsunami warning for Miyakojima in the East China Sea. But the agency later removed the warning.
Photos show collapsed buildings in southern Taiwan after a powerful earthquake. The USGS initially registered it as 7.2, then downgraded it to 6.9.
The three were trapped under the rubble of a building, the island’s official Central News Agency (CNA) reported. A fourth person was rescued.
About 20 passengers were evacuated after a train derailed in the area, but no casualties were reported, the Taiwan Railway Administration said.
A local school also reported damage, said Kolas Yotaka, a former presidential spokesman who is running for local elections in Hualien County.
Taiwanese President Tsai Ing-wen activated Taiwan’s Central Emergency Operations Center after the earthquake. Taiwanese residents have been asked to remain vigilant to avoid potential aftershocks, Tsai Ing-wen said in a recorded statement.
About 110 soldiers were also deployed in Hualien County on Taiwan’s eastern coast to assist with disaster relief efforts, said Sun Lifang, a spokesman for Taiwan’s Ministry of National Defense.