Santorini, the popular Greek holiday island, is taking emergency measures in response to intense seismic activity.

While Greek experts say the quakes, many with magnitudes over 4.5, are not linked to Santorini’s volcano, they acknowledge that the pattern of seismic activity is cause for concern.

Greek authorities have warned of an increase in seismic activity around the Aegean tourist island of Santorini, advising people to avoid four ports, empty their pools, refrain from gathering in indoor spaces and shut schools on Monday.

Greek officials are warning those on the popular tourist island destination of Santorini to stay alert in the coming days due to increasing seismic activity which could mean a strong earthquake is possible.

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.