Why did Venice's Grand Canal turn green? Italian officials now have answer

A mystery stumped Italian officials after the famed Grand Canal in Venice turned bright green over the weekend. 

Italian environmental officials now say the change was caused by the chemical fluorescein.

Storyful reported that "nontoxic chemical is used in underwater construction." However, officials do not believe it was an accident. 

Footage released by the Vigili del Fuoco, Italy’s national firefighters, showed a patch of Venice's famed Grand Canal turning a fluorescent green Sunday morning in the Rialto area.

RELATED: Italian officials stumped after patch of Venice's famed Grand Canal turns fluorescent green

Authorities said the green substance was present on the surface and soluble in the water. Samples were taken at different levels of the surface water body to evaluate how much of the substance tended to settle on the seabed.

Some samples were also carried out in the canals bordering the Rialto Bridge, where the anomalous substance gradually spread, also due to the effect of the tide.

A first analysis of the samples excluded the presence of substances dangerous for the environment, authorities said.

Fluorescein is not dangerous for the aquatic environment and does not contain persistent, bioaccumulative and toxic components.

Under sunlight, fluorescein is able to dissolve after a few days depending on the quantity of powder used. More laboratory investigations will be carried out Monday, authorities said. 

Storyful and Kelly Hayes contributed to this report. This story was reported from Los Angeles.