ROME – The spectacular transformation of a stretch of Venice’s Grand Canal to fluorescent green was due to fluorescein, a non-toxic substance used for testing wastewater networks, the local authorities said on Monday.

Residents noticed a stretch of Venice’s Grand Canal had turned bright green on Sunday, prompting police to investigate amid speculation it could be a stunt by environmentalists.

Analysis showed “the presence of fluorescein in samples taken”, said the Regional Agency for Environmental Prevention and Protection of Veneto.

The results “have not shown the presence of toxic elements in the samples analysed”, the statement said, without specifying the origin of the substance.

This is not the first time the Grand Canal has turned green.

In 1968, Argentine artist Nicolas Garcia Uriburu dyed the waters of the canal green with a fluorescent dye during the 34th Venice Biennale in a stunt to promote ecological awareness. AFP