The Greek authorities scrambled on Thursday to clean up fuel leaked by an oil tanker that sank near Athens, putting popular beaches off limits to swimmers and raising fears of environmental damage.

The Agia Zoni II, a 45-year-old oil tanker, sank early Sunday morning near the island of Salamis, about seven miles from the country’s main port, Piraeus. It was carrying more than 2,500 metric tons of fuel oil and marine gas oil.

Though the leak was initially thought to be contained to the area of the shipwreck, it soon expanded to the coastline area known as the Athens Riviera.