The water in Venice turns fluorescent green near the Rialto Bridge

The Italian fire department said waters in Venice’s main canal turned fluorescent green near the Rialto Bridge, and officials are trying to find the cause.

The Regional Environmental Protection Agency said in a tweet that it had received samples of the altered water and was working to identify the substance that changed the color.

The governor of Venice has called an emergency meeting of the police to find out what happened and consider possible countermeasures, according to Ansa news agency.

Sunday’s incident echoes recent Italian episodes of environmental groups painting monuments, such as using vegetable charcoal to blacken the water of Rome’s Trevi Fountain in protest against fossil fuels.

But unlike previous cases, no activist group has claimed responsibility for what happened in Venice.