ATHENS – A series of earthquakes near the Greek island of Santorini have led authorities to shut down schools, dispatch rescue teams with sniffer dogs and send instructions to residents including a request to drain their swimming pools.

Even though earthquake experts say the more than 200 tremors that have hit the area since early Friday are not related to the volcano in Santorini, which once produced one of the biggest eruptions in human history, locals are on edge.

The strongest earthquake recorded was magnitude 4.6 at 3:55 p.m. Sunday, at a depth of 14 kilometers (9 miles), the Athens Geodynamic institute said. A few tremors of over magnitude 4 and dozens of magnitude 3 have followed. There were no reports of damage or casualties.

Earthquake experts and officials from the Ministry of Climate Crisis and Civil Protection and the fire service have been meeting daily and decided to close schools Monday on the island of Santorini as well as nearby Amorgos, Anafi and Ios.

After Sunday’s meeting, they also advised residents and hotel owners in Santorini to drain their swimming pools over concerns that large volumes of water could destabilize buildings in case of a strong quake.

Another meeting was scheduled Sunday evening at the prime minister’s office with the chief of Greece’s armed forces and other officials.

The fire service sent a contingent of rescuers including a sniffer dog on Saturday, and dispatched more forces Sunday, as a precaution. The rescuers have pitched tents in open fields.

Island residents have been advised to avoid large open-air events and to move about the islands mindful of rockfalls. All four islands have steep cliffs and, in the case of Santorini, a large part on the main town is built on a cliffside.

Experts said it was impossible to predict whether the seismic activity could lead to a stronger tremor, but added that the area could potentially produce a 6 magnitude quake.

Mild earthquakes have also been recorded in Santorini’s volcano caldera, which is mostly undersea, since September. The strongest one with magnitude 3.8 occurred on Jan. 25. Since then, seismic activity inside the volcano has subsided, experts say.

The Santorini volcano eruption at about 1600 B.C. devastated the island, buried a town, and caused massive earthquakes and flooding that impacted the island of Crete and as far as Egypt. Experts estimate that up to 41.3 cubic kilometers (9.8 cubic miles) of rocks were ejected and 9-meter (29-foot) tsunamis hit Crete.

In the 1990s, the Santorini volcano was designated one of 16 volcanoes around the world that need to monitored because of past massive eruptions and proximity to dense population areas.