The water in the Grand Canal, Venice, turned green over the weekend. A non-toxic substance is said to have caused the incident, however, officials have no leads.

Venice’s Grand Canal, a famous tourist attraction in the European city, turned green over the weekend. The mysterious bright green, almost fluorescent color, according to a local official, seems to have been caused by a non-toxic component that in most cases is used to detect leaks of different kinds.

The green water was first visible from Rialto Bridge and gradually moved its way up, due to the tide. The Regional Agency for the Environment in Venice (ARPAV), have reported on the matter, leaving out details on where the colored water emerged from, they further added that the issue would need more testing.

Luca Zaia, the governor of the Veneto region, in a post on social media suggested that there were concerns of a copycat, dyeing the canal green. These concerns come from a similar situation that took place in 1968; the canal was turned green by Nicolas Garcia Uriburu, an Argentinian artist. As per reports from the Metropolitan Museum of Art, he turned the canal green, by using fluorescein as a way to promote ecological awareness. Rivers in other parts of the world, like New York, Paris, and Buenos Aires have also seen Uriburu use them as part of his ecological promotion.

However, Sunday’s incident has still not been claimed by any environmental group.