A magnitude 5.2 earthquake shook the Greek Aegean islands on Sunday, beginning another week of what geologists are calling an extended earthquake swarm that has sent tourists and residents fleeing.

Greek authorities extended school closures Saturday to four islands by one week after recent seismic activity in the region, according to public broadcaster ERT. A committee of officials and experts decided to prolong closures on the islands of Santorini, Ios, Anafi, and Amorgos as a precautionary measure.