A powerful earthquake shook the southern Philippines on Tuesday morning, knocking out power in some areas, sending people out of homes and buildings and forcing classes to be suspended in one city to allow inspections of school buildings.

There was no immediate reports of major damage or injuries from the quake, which the Philippine Institute of Seismology and Volcanology said had an initial magnitude of 6.6 and was caused by movement in a local fault about 7 kilometers (4.3 miles) deep about 25 kilometers northeast of Tulunan town in Cotabato province. The U.S. Geological Survey reported that the earthquake had a magnitude at 6.8.

Davao city Mayor Sara Duterte suspended school classes to allow authorities to inspect buildings for possible damage after the latest quake to hit the region in recent weeks.

A 6.3 earthquake earlier this month in the same region killed five people and caused damage to several schools and other buildings.

In July, two earthquakes hours apart struck a group of sparsely populated islands in the Luzon Strait in the northern Philippines, killing eight people.

Seismic activity is common in the Philippines, which lies on the Pacific “Ring of Fire,” the ring of faults around the Pacific Ocean where most of the world’s earthquakes occur.

A magnitude 7.7 quake killed nearly 2,000 people in the northern Philippines in 1990.

(AP)