A magnitude 7.7 earthquake struck off the coast of Flores Island in Indonesia’s East Nusa Tenggara province early Saturday. It killed at least 20 people and set off a tsunami warning that was lifted within hours.

The quake hit at 5:58 a.m. local time. Its epicenter sat about 68 kilometers north-northwest of the city of Ende, Indonesia’s geophysics agency said. Three aftershocks followed within the first half hour, measuring 5.9, 5.6 and 6.1 in magnitude.

East Nusa Tenggara’s governor put the early death toll at five as rescue crews reached the first villages. By Saturday evening, wire services including Al Jazeera and Kyodo News put the confirmed toll at 20. Officials warned the number would likely climb once rescue teams reached more remote villages.

Around 2,000 residents in the Nagekeo district evacuated to higher ground after the tsunami alert went out. Houses, warehouses, schools, health facilities and government offices across the affected region sustained damage, though a full accounting is still underway.

Indonesia’s Meteorology, Climatology and Geophysics Agency, known locally as BMKG, issued the warning for several coastal areas. It stood the alert down within hours, saying wave activity had not reached dangerous levels.

Indonesia sits on the Pacific Ring of Fire, where the Eurasian, Pacific and Australian plates meet. That makes the archipelago one of the most earthquake-prone places on earth. Flores was struck by a deadly quake and tsunami in 1992 that killed more than 2,000 people, a disaster still remembered across the region.

The swift warning shows how seriously Indonesian authorities now treat undersea quakes. Memories of the 2004 Indian Ocean tsunami still run deep. That disaster, triggered by a magnitude 9.1 quake off Sumatra, killed roughly 230,000 people region-wide, more than 170,000 of them in Indonesia.

Indonesia’s national disaster agency said search and rescue crews were still working through damaged buildings Saturday night. Aid convoys were headed toward the hardest-hit villages near Ende.