According to officials of the Greek Ornithological Society, an analysis conducted by British labs showed the birds were killed by clostridium botulinum, the spore-forming rod that produces the potent neurotoxin which causes botulism.

The finding supports the suspicions of local officials that the outbreak at Lake Koronia was caused by extensive draining of the lake for farming purposes as clostridium botulinum develops in stagnant or polluted waters.

Despite the fact that it is supposedly protected as wildlife area, Lake Koronia has lost a third of its surface in the last 30 years.

Foodbourne ingestion of the botulism neurotoxin has a high mortality rate for humans if not treated immediately. Wild water fowl and some fish are also known to be affected.

At least 4,500 birds and 1,000 fish are known to have died at the lake, paralysed by the substance. Twenty-nine species of birds, including several protected ones, were hit. The dead include some 150 pelicans as well as gulls and ducks.

Officials have stopped the deaths by scaring away birds that tried to approach Koronia. Heavy rainfall in recent days added fresh water to the lake and helped dissolve the toxin, Salonika deputy prefect Yiannis Bikos told AFP.

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