Pakistan, July 29 -- A powerful 6.8-magnitude earthquake struck Japan's southern Kyushu island, killing at least 13 people and injuring dozens after a shopping mall partially collapsed following an explosion believed to have been triggered by the quake.

Read More: Japan earthquake rocks Kumamoto, casualties feared

The earthquake hit Kumamoto Prefecture on Tuesday, prompting a tsunami warning that was later lifted. Rescue operations continued overnight as emergency crews searched for survivors trapped beneath the rubble of the damaged Aeon Mall Kumamoto.

Authorities said an explosion of unknown origin tore through the shopping center about an hour after the earthquake. Investigators are examining whether a gas leak caused the blast. Eig...