That’s what staff discovered at the cafeteria of a daycare centre for single mums and their infant children near Lille in the north of France.
The centre in Lambersart was closed on Thursday after the toxic fluid was found in the food, the Voix du Nord newspaper reported.
Two adults tasted the mashed potatoes and suffered major burns, the newspaper reported.
No child came into contact with the adulterated food.
The daycare centre accommodates children under the age of three with their mothers.
An investigation has been launched to determine whether the presence of the cleaning fluid was accidental or criminal.