Greek authorities scrambled today 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 Sept. 10 near the island of Salamis, about 7 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.

Evaggelia Simou, a resident of Salamina, on the island, denounced authorities for not tackling the oil spill more quickly and fully.

“We drove by the Selinia beach on Sunday night, and were alarmed because of the suffocating smell of oil,” Simou said in a Facebook chat.

When she and her husband went to the beach, they were shocked to see that a thick coat of oil had blackened the water.

“Huge pieces of floating tar were burdening the waves, dead fish floated on the surface,” Simou said. They were surprised to see no cleanup workers, she said.

Simou returned to the beach Monday morning, along with her son, and was stunned to see no sign of an active cleanup, more than 24 hours after the shipwreck.

Thick, black masses of oil had reached the beaches around Glyfada, a high-end seaside community south of Athens, by Sept. 13.

George Papanikolaou, mayor of Glyfada, said he got a phone call from the Piraeus harbor master warning of the spill only a few hours before the black ooze washed up.

“The vessel sank on Sunday. How is it possible that the leak reached Glyfada from Salamina?” Papanikolaou asked in a phone interview. “And how is it possible that we only heard about it on Wednesday?”

Since then, three private anti-pollution vessels have cleaned up more than 180 metric tons of fuel from Glyfada’s four beaches. Just this summer, one of the beaches had been recognized by the Foundation for Environmental Education as a Blue Flag beach, a certification of water quality.

“It’s tragic that it happened now, after all four beaches have gotten so beautiful,” Tima Vlasto, 51, an American who has lived in Glyfada for six years, said in a phone interview. “Seeing this makes you want to leave. If I can’t swim here, what’s the point of living in Glyfada?”

Papanikolaou said that emotions were running high in his community.

“We’re angry,” he said. “It’s just such a shame that all this hard work can be destroyed in a split second.”

Some ecologists have called the oil spill an environmental disaster, with immediate and potential long-term effects.

One photo circulating on the internet showed a kingfisher drenched in black oil. The bird tried to feed itself by fishing in the polluted waters, but quickly died because of the oil, according to Konstantina Ntemiri, an officer of the Hellenic Ornithological Society.

The full extent of the pollution and its effects are not yet clear; areas like uninhabited rocky islets are also thought to be affected.

Panagiotis Kouroumplis, the Greek shipping minister, suggested Thursday that he would resign if asked by Prime Minister Alexis Tsipras. But as the political opposition insisted that he step down, the ministry said his words had been taken out of context.

After touring the affected areas in a Coast Guard vessel, Kouroumplis said that there had been “significant improvement” and that “in just a few days this affair will have been forgotten.”

That view is not shared by Themis Labridis, 33, a filmmaker whose family home is in Palaio Faliro, between Piraeus and Glyfada.

“We couldn’t sleep because of the smell,” he said in a phone interview. “The sea is like a dirty lagoon, a swamp of oil.”

On Thursday, he went with a friend to nearby Alimos beach, where they met another volunteer and used buckets to remove big pieces of black tar from the water.

They also gathered blackened stones from the shore. No authorities were around to stop — or help — them. “Who is going to clean the beaches of each and every polluted stone?” Labridis asked.

The cause of the shipwreck remains unclear.

The Hellenic Register of Shipping, an independent organization that oversees shipping safety, said that the tanker had not been certified as seaworthy, although its owner, Fos Petroleum, said that it had all of the proper credentials. The Greek Ministry of Shipping and Island Policy did not respond to several requests for information.