Venice police investigate why Grand Canal turned bright green

Gondoliers seen boating through phosphorescent water on Sunday

A gondola skirts the patch of phosphorescent green water in Venice's Grand Canal on Sunday. AP

Police in Venice are investigating the source of a substance that turned the water in the city’s Grand Canal bright green on Sunday.

Gondoliers could be seen paddling through the phosphorescent water as tourists took photographs of the green patch of water, which began at the Rialto Bridge, extending along part of the canal.

The area’s governor, Luca Zaia, shared a picture of the scene near the arched Rialto on Sunday.

“This morning in #CanalGrande of #Venezia a patch of phosphorescent green liquid appeared, reported by some residents near the Rialto Bridge,” he wrote on Twitter.

“The prefect has convened an urgent meeting with the police force to investigate the origin of the liquid.”

It was initially reported by residents.

Newspaper La Nuova Venezia said police were looking into whether it was a stunt by climate change activists.

Images shared on social media show a bright section of green in the canal along an embankment lined with restaurants.

Mr Zaia said officials had requested that police investigate to determine who was responsible. Environmental authorities were also testing the water.

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

The Grand Canal is one of the major waterways in the city, stretching from the lagoon to the basin at San Marco.

It is lined with more than 170 buildings, most of which were built between the 13th and 18th century by wealthy Venetian families.

The water in the city's canals comes from the Venetian Lagoon, which is an enclosed bay of the Adriatic Sea.