MANILA, Philippines (AP) — Rescuers dug with picks and shovels trying to reach dozens of people trapped under houses collapsed by a strong earthquake today that shook a central Philippine island and set off landslides.

At least 13 people were killed and 40 are believed missing, most of them along the shore near the epicenter of the 6.9-magnitude quake that struck in a narrow strait just off Negros Island.

In the mountain village of Planas, 9 miles ( 15 kilometers) from coastal Guihulngan town in Negros Oriental province, as many as 30 houses were buried with at least 40 residents believed trapped, said Gov. Roel Degamo.

“ Their situation is bad because if you are covered by landslide for one hour, two hours, how can you breathe?” Mayor Ernesto Reyes said. “But we just hope for the best, that there are still survivors.”

Army troops and police were deployed to help in the rescue.

At least 10 people were confirmed dead in Guihulngan, including students at a college and an elementary school and others in a town market that collapsed, Reyes said. About 100 were injured.

The quake, which hit at 11:49 a.m. (0349 GMT), triggered another landslide in the mountain village of Solongon in La Libertad town, also in Negros Oriental. An unknown number of people were trapped, said La Libertad police chief inspector Eric Arrol Besario.

“We’re now getting shovels and chain saws to start a rescue because there were people trapped inside. Some of them were yelling for help earlier,” Besario told The Associated Press by phone. Three key bridges in the town cracked and were no longer passable, he said.

Nine bridges were damaged in Negros Oriental, including four that were not passable, said Gov. Degamo.

The worst damage was concentrated in the province’s mountainous northern portion, he said.