Fluorescein is a non-toxic substance generally used for tests on wastewater networks. The results "did not demonstrate the presence of toxic elements in the samples analyzed," local authorities said.
The change of color had been reported by residents, raising many questions. In 1968, the Argentine artist Nicolas Garcia Uriburu dyed his waters green with a fluorescent dye during the 34th Venice Biennale, as part of an ecological awareness campaign. The police have sought to know if climate activists could be behind the phenomenon.