A group of amateur Israeli divers have stumbled upon the largest collection of medieval gold coins ever found in the country, dating back to the 11th century and likely from a shipwreck in the Mediterranean Sea.

The Israel Antiquities Authority said Wednesday that the find consists of 2,000 coins, weighing about 6 kilograms (13 pounds).

Kobi Sharvit, director of the authority's marine archaeology unit, says the coins were likely swept up in recent storms near the Israeli port city of Caesarea.

He says they probably came from a boat that sank on its way to deliver tax money to Egypt about 1,000 years ago, or that it came from a merchant ship trading among Mediterranean coastal cities.

He says it's a "fascinating and rare historical evidence" from the Fatimid era.