JAKARTA-A powerful magnitude 7.7 earthquake struck eastern Indonesia early Saturday, killing at least 38 people and causing significant damage across the island of Flores.

The U.S. Geological Survey says the earthquake was centered about 42 miles north-northwest of Ende, Indonesia, at a depth of about 6 miles. The shallow earthquake caused strong shaking, damaged and collapsed buildings, and triggered landslides that blocked roads and made it difficult for rescue crews to reach some communities.

A tsunami warning was issued after the earthquake, sending residents in coastal areas fleeing to higher ground. The warning was later lifted after officials found no significant tsunami threat. Small tsunami waves of less than three feet were reported.

Thousands of people have evacuated their homes, while power outages and communication problems are complicating the emergency response. Officials say the death toll could continue to rise as crews reach areas that have been difficult to access.

A series of powerful earthquakes

The Indonesia earthquake comes just days after a magnitude 7.4 earthquake struck western Colombia on August 10. That earthquake has killed hundreds of people and caused widespread destruction across the country. Rescue crews were still searching for survivors Friday as the death toll continued to climb.

It also follows a magnitude 7.3 earthquake that struck southern Mexico on July 17. That earthquake was centered near the Pacific coast close to the Guatemala border and was felt across a wide area, including parts of Mexico and Central America.

All three earthquakes occurred along or near the Pacific Ring of Fire, a zone around the Pacific Ocean where several tectonic plates meet and earthquakes and volcanic activity are common.

The recent earthquakes are a reminder of how active this part of the world can be. The USGS catalog shows numerous magnitude 6 and larger earthquakes around the Pacific region in recent months, including events in Japan, the Philippines, Indonesia, Mexico and other parts of the Pacific.

Scientists do not consider the recent earthquakes to be evidence that one earthquake caused another. Large earthquakes occur independently as stress is released along different faults and plate boundaries.

Rescue and recovery efforts are continuing in Indonesia as officials work to determine the full extent of the damage.