Some 10 tons of dead fish have been found in Ismarida Lake in the Rhodope prefecture, northeastern Greece, with experts finding that there is a lack of oxygen in some parts of the body of water.

The head of the lake’s managing body, Manos Koutrakis, said authorities were baffled as to why there should be an absence of oxygen in the lake.

They ruled out the possibility that the fish had been killed by fishermen using dynamite.