09/05/2012 12:25 EDT | Updated 11/05/2012 05:12 EST

Powerful Costa Rica quake triggers tsunami warning

A magnitude-7.6 earthquake has shaken Costa Rica and triggered a tsunami warning, the U.S. Geological Survey said.

The quake struck at 8:42 a.m. local time Wednesday and was centred in the northwestern province of Guanacaste, at a depth of 40 kilometres, the USGS said.

In the coastal town of Nosara in northwest Costa Rica, trees shook violently, light posts swayed and teachers chased primary school students outside.

There were no immediate reports of casualties, but local media reported serious damage in Guanacaste.

A tsunami warning was issued for the western Pacific but was later reduced to Costa Rica, Nicaragua and Panama, the Pacific Tsunami Warning Center said.