Experts warned on Tuesday that the earthquake-hit volcanic island of Sao Jorge, in Portugal's Azores archipelago, could see an eruption like that of Spain's La Palma, which destroyed thousands of properties and crops over 85 days.
The lush mid-Atlantic island has been rattled by more than 20,000 small earthquakes, which reached a magnitude of up to 3.3, in the past 11 days.
The tremors could herald a volcanic eruption for the first time since 1808, or a powerful earthquake, said the region's CIVISA seismo-volcanic surveillance centre.
Elderly people and those with reduced mobility have been evacuated from Velas, the municipality where most of the seismic activity has been recorded, and many locals have left the island in fear. "The magnitude of the earthquakes has reduced slightly... but the population must stay alert, they should not relax," said Eduardo Farias, head of Azores' Civil Protection authority.
At a school in Velas, classes were suspended and some of the school's rooms will be turned into a health center.
Francisco Fonseca, president of Sao Jorge's health service, said health workers with experience working in natural disasters have been deployed to the island.
"This whole situation is a challenge," he said. "It is distressing and out of the ordinary."
Sao Jorge's sudden increase in seismic activity is reminiscent of the earthquakes detected before the eruption of the Cumbre Vieja volcano on Spain's La Palma island last year, some 1,400 km (870 miles) southeast of the Azores.
Experts at the Canary Islands Volcanology Institute, Involcan, which monitored the La Palma eruption, said on Tuesday about 20 million cubic meters of lava could be spewed out on Sao Jorge if an eruption takes place.
Luca D'Auria, director of Involcan's volcanic surveillance department, told Reuters a soil deformation caused by the volcanic activity had been detected in Sao Jorge.
"It could either end in nothing (...) or it could end in a volcanic eruption," he said.
Farias said CIVISA would analyse Involcan data but asked Sao Jorge's about 8,400 residents not to panic.
