Europe’s biggest mushroom has been discovered in Switzerland's only national park.
Scientists said on Friday the fungus was about 1,000 years old and measured 800 by 500 metres, the equivalent of 100 football fields.
A detailed survey revealed that the fungus was a single mushroom, mostly concealed underground. It was found near the Ofenpass in the mountainous southeastern canton of Graubunden.
“The majority of the fungus is an underground network that looks a bit like shoelaces,” said Muriel Bendel, spokeswoman for the Swiss Federal Institute for Forestry, Snow and Landscape Research.
“The surface mushrooms look like the normal type you would pick, and are brown to yellow.”
The fungus, "Armillaria ostoyae", is more commonly known as the honey mushroom, and is edible, according to the researchers.
They added that the mushroom had been known since Roman times for its cleansing effects on the digestive tract, provided it was eaten raw. But certain forms can kill trees.
The institute said Switzerland's monster mushroom was trumped only by a growth in the United States which covers a surface area of nine square kilometres and weighs an estimated 600 tons.
swissinfo with agencies
Mushrooms are the spore-bearing structures of fungi, which derive energy by decomposing plant and animal material.
There are estimated 300,000 species, although only 100,000 have been identified.
Yeast and penicillin are both forms of fungi.