SANTORINI, Greece (AP) — Schools were closed and emergency crews deployed on the volcanic Greek island of Santorini on Monday after a spike in seismic activity raised concerns about a potentially powerful earthquake.

Precautions were also ordered on several nearby islands — all popular summer vacation destinations — after more than 200 undersea earthquakes were recorded in the area over the past three days.

“These measures are precautionary, and authorities will remain vigilant,” Civil Protection Minister Vasilis Kikilias said late Sunday following an emergency government meeting in Athens. “We urge citizens to strictly adhere to safety recommendations to minimize risk.”

While Greek experts say the quakes, measuring up to magnitude 4.7, are not linked to Santorini’s dormant volcano, they acknowledge that the pattern of seismic activity is cause for concern.

Fire Service rescue teams with sniffer dogs arrived Sunday and established tents in open areas. Residents and visitors were advised to avoid large indoor gatherings, while hotels were instructed to drain swimming pools to reduce potential building damage from an earthquake.

Crescent-shaped Santorini, which is slightly larger than Manhattan, is a premier tourism destination with daily arrivals via commercial flights, ferries, and cruise ships. The island draws more than 3 million visitors annually to its whitewashed villages, built along dramatic cliffs formed by a massive volcanic eruption more than 3,500 years ago.

Prominent Greek seismologist Gerasimos Papadopoulos cautioned that the current earthquake sequence – displayed on live seismic maps as a growing cluster of dots between the islands of Santorini, Ios, Amorgos, and Anafi — could indicate a larger impending event.

“All scenarios remain open,” Papadopoulos wrote in an online post. “The number of tremors has increased, magnitudes have risen, and epicenters have shifted northeast. While these are tectonic quakes, not volcanic, the risk level has escalated.”

In Santorini’s main town of Fira, local authorities designated gathering points for residents in preparation for a potential evacuation, though Mayor Nikos Zorzos emphasized the preventive nature of the measures.

“We are obliged to make preparations. But being prepared for something does not mean it will happen,” he said during a weekend briefing. “Sometimes, the way the situation is reported, those reports may contain exaggerations... so people should stay calm.”