ATHENS, Greece (AP) — Scientists say a collection of structures discovered in shallow waters off the Greek island of Zakynthos were actually formed by natural process.

Divers found the site three years ago and dubbed it the "lost city" because the structures resemble remains of ancient walls and pillars, as well as doughnut-shaped rings.

But after examining the site in detail, researchers from Greece and Britain said Friday that the structures are the result of microbes feeding off underwater methane vents, leaving mineral deposits.

The process, known as concretion, is estimated to have happened up to 5 million years ago.

The scientists, led by Julian Andrews of the University of East Anglia in England, concluded that when it comes to exciting underwater discoveries "columns and pavements in the sea, not always antiquities will be."