An underwater volcanic eruption threatens one of the Canary Islands and led to the evacuation of some residents.

Officials said Tuesday at least 500 people from the small coastal town of La Restinga on El Hierro island were relocated as a precaution.

Experts said the initial underwater eruption was not visible and could not be felt, but large numbers of dead fish were a clue to the eruption. Recent seismic activity suggests another eruption may occur closer to the island.

Experts said they think the underwater volcano began erupting Monday. The volcano is located five kilometers off the coast at a depth of up to 1,200 meters.

The Canary Islands formed from underwater volcanic activity approximately 23 million years ago.