WELLINGTON, New Zealand – A powerful 7.1-magnitude earthquake struck much of New Zealand’s South Island early Saturday and caused widespread damage, but there were just two reports of serious injuries. Looters broke into some damaged shops in Christchurch, police said.

The quake, which hit 19 miles west of the southern city of Christchurch according to the state geological agency GNS Science, shook a wide area, with some residents saying buildings had collapsed and power was severed. No tsunami alert was issued.

GNS Science initially reported the quake as magnitude 7.4, but later downgraded it after re-examining quake records. The U.S. Geological Survey measured the quake at 7.0.

Christchurch Mayor Bob Parker declared a state of emergency four hours after the quake rocked the region, warning people that continuing aftershocks could cause masonry to fall from damaged buildings.

Minister of Civil Defence John Carter said a state of civil emergency was declared as the quake was “a significant disaster,” and army troops were on standby.

Parker said the “sharp, vicious earthquake has caused significant damage in parts of the city with walls collapsed that have fallen into the streets.”

Chimneys and walls had fallen from older buildings, with roads blocked, traffic lights out and power, gas and water supplies disrupted, he said.

“The fronts of at least five buildings in the central city have collapsed and rubble is strewn across many roads,” Christchurch resident Angela Morgan told The Associated Press.

“Roads have subsided where water mains have broken and a lot of people evacuated in panic from seaside areas for fear of a tsunami,” she said, adding that “there is quite significant damage, really, with reports that some people were trapped in damaged houses.”

Christchurch Hospital said it had treated two men with serious injuries and a number of people with minor injuries.

One was hit by a falling chimney and was in serious condition, while a second was badly cut by glass, hospital spokeswoman Michele Hider said.

Christchurch police reported road damage in parts of the city of 400,000 people, with a series of sharp aftershocks rocking the area. Police officers cordoned off some streets where rubble was strewn about. Video showed parked cars crushed by heaps of fallen bricks, and buckled roads.

“There is considerable damage in the central city and we’ve also had reports of looting, just shop windows broken and easy picking of displays,” Police Inspector Mike Coleman told New Zealand’s National Radio.

Police Inspector Alf Stewart told the radio that some people had been arrested for looting.

“We have some reports of people smashing (storefront) windows and trying to grab some property that is not theirs we’ve got police on the streets and we’re dealing with that,” he said.

Suburban dweller Mark O’Connell said his house was full of smashed glass, food tossed from shelves, with sets of drawers, TVs and computers tipped over.

“She was a beauty, we were thrown from wall to wall as we tried to escape down the stairs to get to safety,” he said. “It was pitch black (with the power cut) and we walked through smashed glass everywhere on the floor.”

The quake hit at 4:35 a.m. shaking thousands of residents awake, New Zealand’s National Radio reported.

New Zealand sits above an area of the Earth’s crust where two tectonic plates collide. The country records more than 14,000 earthquakes a year — but only about 150 are felt by residents. Fewer than 10 a year do any damage.