At least 20 people were killed on Saturday after a 7.7-magnitude earthquake struck just off the coast of an island in eastern Indonesia, officials said.

The earthquake hit north of Flores Island, the United States Geological Survey said. It caused several buildings to collapse on the island, and was one of the largest the area had experienced in decades, said Wijayanto, the director of earthquake and tsunami affairs at the Meteorology, Climatology, and Geophysics Agency in Indonesia.

“An earthquake like this occurred in 1992 with a magnitude of 7.5, causing immense damage,” Mr. Wijayanto, who, like many Indonesians, goes by one name, said in a statement. He added that the authorities would continue to monitor for aftershocks.

Fathur Rahman, the chief of the search and rescue office in Maumere, one of the largest towns on Flores Island, said his team had confirmed 20 deaths and was still searching for people who could be buried under rubble.

Indonesia, an archipelago with about 17,500 islands, is at the edge of the Pacific Ocean, in an area known as the Ring of Fire. The region experiences frequent earthquakes and volcanic eruptions as large blocks of the Earth’s crust collide. More than 2,000 people were killed in 2018 after a 7.5-magnitude earthquake and ensuing tsunami devastated central Indonesia.

The authorities initially issued a tsunami warning on Saturday, but soon after said the threat had passed.

The quake struck about 42 miles northwest of Ende, the regional capital, according to data from the United States Geological Survey. Several aftershocks were reported in the area in the hours after the temblor, including one with a magnitude of 6.1. The authorities warned that more could occur in the coming days.

Rin Hindryati contributed reporting.