Repeated earthquakes are rattling Greece’s volcanic island of Santorini. The quakes are prompting authorities to dispatch rescuers with tents, a sniffer dog and drones and to shut down schools on four islands.

In Fira, Santorini’s main town, local authorities have set up gathering points for residents though no evacuation orders are in place right now. However, it’s been agreed by seismologists that these quakes could be an indicator of an impending seismic event.

More than 200 tremors have been registered since Friday between the volcanic islands of Santorini and Amorgos, the civil protection ministry said in a statement on Sunday, citing experts tasked with assessing earthquake risks and monitoring Greece’s volcanic arc.