Earthquakes are still rattling Greece’s volcanic island of Santorini every few minutes as authorities bolster their emergency plans in case the hundreds of temblors in recent days are a harbinger of a larger quake to come.

Greece sits on multiple fault lines and is often rattled by earthquakes. Santorini is visited by about three million people annually, including many British tourists. One of the largest volcanic eruptions in history, around 1600 BC, formed the island in its current shape, while the last eruption in the area occurred in 1950.

Thousands of people fled the Greek island of Santorini by sea and air for a third day on Tuesday, as more earthquakes shook the top travel destination.