WELLINGTON, New Zealand - A tsunami warning was issued by the U.S. Geological Survey after a 7.8-magnitude earthquake struck off New Zealand's western coast Wednesday.

The quake's epicenter was 100 miles (161 kilometers) west of Invercargill, off the west coast of New Zealand's South Island at a depth of 21 miles (33 kilometers). It hit at 0922 GMT on Wednesday, the USGS said.

The Pacific Tsunami Warning Center in Hawaii sent an e-mail alert warning of a possible tsunami in New Zealand.

"An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines in the region near the epicenter within minutes to hours," the warning center said.

The quake was felt widely across South Island, where the earthquake was centered.

Police in the town of Tuatapere on South Island said they had reports of minor cracks in buildings and stock falling from supermarket shelves.

However, no reports of serious damage or injuries have been received so far, police said.