A river in Japan turned bright green overnight after chemicals used in the bath salt-making process were dumped into the water.

Concerned residents in Ikoma City, Nara Prefecture, alerted authorities after the Tatsuta River turned bright green.

Ikoma City's Environmental Conservation Division launched an investigation and warned against locals using the river.

They found that large quantities of sodium fluorescein had been dumped by the river bank, which is red - but turns green when coming in contact with water.

Ikoma City officials released a statement: "There were traces of a red substance dumped into the river from the road, and it was recognized that the substance left on the road turned green when water was poured on it.

"It is believed that this caused the river water to become coloured.

"Sodium fluorescein, the main component of colouring agents used in bath salts, was detected.

"The Safety Data Sheet for Sodium Fluorescein states that there are no physical or chemical hazards or health hazards.

"In addition to the names and physicochemical properties of chemical substances contained in chemical products, dangers, toxicity, first aid measures in case of exposure, handling methods, storage methods, disposal methods, etc.

"Since the safety of the water was confirmed by the announcement from Nara Prefecture, we have lifted the warning against using water for agricultural purposes."

The Tatsuta River is described as a picturesque body of water that connects multiple towns and cities in the region.

The footage was captured on July 5.