The Greek island has a long history of earthquakes, but what is causing the recent series of quakes has scientists perplexed.

Multiple earthquakes are rattling Santorini, a volcanic island in Greece, prompting authorities to dispatch rescuers with tents, a sniffer dog and drones, and to shut schools on four islands. Residents have been warned to avoid indoor gatherings,

A state of emergency was declared on Santorini Thursday after a magnitude 5.2 earthquake shook the Greek island late Wednesday. The tremor is the latest — and strongest — in a series of quakes that have struck the island since last week,