AFP reported that hospitals in the Lot region admitted 21 people on Friday with stomach pains, diarrhoea and vomiting. In Tarn-et-Garonne, 30 cases have been reported in the last two weeks. Health officials say many more are likely to have been poisoned but have not sought treatment.
The cases are linked to people, particularly tourists, eating the wrong type of mushrooms.
The mushroom crop usually appears in September but a warm spring and high rainfall in July have caused it to come early this year.
A particular species of the boletus mushroom, which looks similar to an edible mushroom but turns blue on cutting, is thought to be the culprit.
"Holidaymakers see the locals collecting mushrooms and try to do the same thing, without really knowing what they're doing," Xavier Binetti, a hospital doctor in Cahors, told AFP.
The consequences of eating this particular mushroom tend to be uncomfortable rather than dangerous, although they can be more serious for children and older people. Doctors advise staying hydrated and waiting for the symptoms to pass.