MOSCOW (AP) — Russian prosecutors on Wednesday opened a criminal probe into an oil spill off the country's Black Sea coast that appeared to be far bigger than initially expected.

The spill occurred over the weekend at the oil terminal in Yuzhnaya Ozereyevka near the port of Novorossiysk that belongs to the Caspian Pipeline Consortium, which pumps crude from Kazakhstan. The oil spilled while being pumped into the Minerva Symphony tanker, which sails under the Greek flag.

Authorities initially estimated that the spill covered only about 200 square meters (2,153 square feet), but Russian scientists said Wednesday after studying satellite images that it actually covered nearly 80 square kilometers (nearly 31 square miles).

WWF Russia has estimated that about 100 metric tons of oil have spilled into the sea.

The Prosecutor General's office has opened a criminal probe on charges of environmental pollution and said it would seek damages.