Venice, Italy - A shimmering green liquid in Venice's famous Grand Canal has caused a stir in the lagoon city. On Sunday, the water near the Rialto Bridge suddenly glowed green, with no initial explanation.

The Italian fire brigade said it had taken samples together with the environmental protection agency ARPA and was examining them.

The prefect of Venice immediately called an emergency meeting with the police to investigate the incident.

The president of Veneto, the region around Venice, Luca Zaia, shared via his Twitter account on Monday that the green liquid is most likely not dangerous.

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ARPA Veneto experts determined after evaluating the samples that it was probably a coloring, organic agent.

This is used in water inspections or cave research, Zaia said, adding that there is no danger of water contamination.

Some Venetians recalled the year 1968, when the artist Nicolás Garcia Uriburu from Argentina dyed the water of the city's central canal green to draw attention to water pollution.

Because more and more climate activists in Italy have recently been conspicuous with their color campaigns, there were also suspicions that this could be such a protest – but at first no one claimed responsibility.

Zaia criticized that Venice had become a "staging ground for activism."

On Whit Sunday, the traditional regatta Vogalonga took place in Venice, in which rowing boats, canoes, and gondolas participate. It was launched in 1974 as a protest against motorboats.