A magnitude 8.7 earthquake struck off Indonesia's Sumatra Island late Monday evening near the area where a similar earthquake triggered a tsunami last December that killed 300,000 people across the Indian Ocean.
Countries from Indonesia to Sri Lanka warned coastal residents to move to high ground after the quake struck late Monday at 11:09 p.m. local time.
The U.S. Geological Survey says the quake struck 200 kilometers northwest off Sibolga, close to where the 9.0 earthquake struck on December 26. That earthquake triggered tsunami waves that nearly wiped out thousands of villages in a dozen Indian Ocean countries.
U.S. experts warned that the tsunami risk was high. However, some experts were saying the location of Monday's earthquake may mean that any destructive waves would flow farther south, toward Mauritius, and away from the areas hardest hit in December.
About two hours after the quake struck, there were no reports of tsunami waves. In Thailand, officials said it appeared the risk had passed but urged citizens along the coast to be cautious.
J. Radakrishnan is the chief district official for the town of Nagapattinam on India's southeast coast, which was hit hard in December.
"We have conflicting reports. But as a precaution people have moved to safer places. And we are also on our rounds and we are monitoring the situation," he said.
It appeared the worst damage from Monday's quake was on Indonesia's Nias Island, off the west coast of Sumatra. There were reports of dozens of deaths there.
U.S. diplomats around the region have been alerted to be ready to lend any assistance necessary. The United Nations also is monitoring the situation.
Since December, countries in Asia have discussed establishing a tsunami warning system to cover the Indian Ocean. However, a debate over where to locate the system's control center and the immediate need to rebuild shattered communities has meant no action has been taken to set up the system.