A 7.1-magnitude earthquake struck New Zealand's South Island early Saturday and caused widespread damage, but no deaths and only two serious injuries were reported. Looters broke into some damaged shops in Christchurch, police said.

The powerful quake hit 19 miles west of Christchurch, the South Island's largest city, according to the state geological agency GNS Science. It shook a wide area, knocked out power, and many buildings had at least partially collapsed. No tsunami alert was issued.

GNS Science initially reported the quake's magnitude as 7.4 before downgrading it. The U.S. Geological Survey measured it at 7.0.