A river in western Japan suddenly turned bright lime green Wednesday morning, concerning locals and prompting a quick investigation. 

Video shared on social media and obtained by Reuters shows a local woman walking her small dog along the strangely-colored Tatsuta River in Nara Prefecture's Ikoma city. The woman told Reuters that the situation was concerning. 

The Tatsuta River connects multiple areas in the region – Ikoma City, Heguri Town and Ikaruga Town – and is known as a "picturesque destination mentioned in poetry since ancient times," according to travel company Navitime. The river is also known for being a "famous place to view fall foliage," the company says. It's been depicted in the paintings "Autumn: The Tatsuta River," which is kept at the Philadelphia Museum of Art, and the 1853 painting "Yamato Province: Tatsuta Mountain and Tatsuta River (Yamato, Tatsutayama, Tatsutagawa)."

The colored water was first reported at 5 a.m. local time, and by 6:30 a.m., the city's Environmental Conservation Division had arrived to inspect further. Initially, officials warned against people using water from the river for agricultural purposes. 

But by Wednesday evening local time, officials revealed that the cause for the sudden color change was sodium fluorescein, "the main component of coloring agents used in bath salts," according to officials. There had been traces that the red substance had been dumped into the river, they said, that "turned green when water was poured on it." 

According to the National Institutes of Health, sodium fluorescein is "an orange-red to dark red powder" that doesn't have an odor or a taste. 

There were no reports of any health effects from the river, and officials say that the substance is not known to cause any hazards. Officials lifted their warning against its agricultural use. 

The incident comes just days after another body of water in Japan changed into an odd color. Last week, water at a port in Okinawa's Nago city turned blood red, BBC News reported, with some describing it as a "gruesome" and "venomous" transformation. 

Propylene glycol, which the CDC describes as a "synthetic liquid substance that absorbs water," had leaked into the river from local company Orion Breweries' cooling system. The CDC says that the substance "can mix completely with water" and breaks down "relatively quickly" – within several days to a week in water and soil. 

In:
• Environment
• Japan

Li Cohen

Li Cohen is a social media producer and trending content writer for CBS News.

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