The Greek island of Santorini is being rattled by dozens of tremors, prompting authorities to close schools and airlines to announce additional flights on Monday to help people leave the popular tourist destination.

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.

Authorities have heightened precautions on Santorini, Greece, following over 200 undersea earthquakes, some up to 4.8 in magnitude, raising earthquake concerns. Schools are closed, and emergency protocols activated for Santorini and nearby islands.