Water in the main canal of Venice turned fluorescent green on Sunday, and authorities are trying to determine the cause. This information was reported by Reuters, citing the Italian Fire Department.

The agency notes that the incident is reminiscent of recent episodes in Italy when environmental activist groups painted monuments, including using vegetable charcoal to dye the water of the Trevi Fountain in Rome black as a protest against fossil fuels. However, unlike previous cases, no activist group has claimed responsibility for what happened in Venice.

The Regional Environmental Protection Agency of Italy has collected water samples and is attempting to identify the substance that caused the color change.