Residents of a small Russian city were startled after a small river suddenly turned bright green recently, according to local reports. 

Locals are calling for tests amid toxic pollution fears in the waterway in Penza, located 400 miles southeast of Moscow. 

"A poisonous green creek on Gagarin Street worries residents of Penza," the Mash media outlet reported. "The local administration is already studying the liquid."

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Footage shows bright-green water flowing amid a snow-covered landscape. 

The river was hit by a sewage overflow in 2020, but the water never turned green, the news outlet said. 

The All-Russia People's Front, a political coalition started in 2011 by then-Prime Minister Vladimir Putin, has been looking for violators of environmental regulations, the report said. 

The likely cause was an "accident," Mash reported. The Moskovsky Komsomolets media outlet reported that the cause of the sudden coloration was due to "industrial dumping."

Penza is home to 17 manufacturing plants, including some that make items for the nuclear power industry, radio and communications equipment, and automated management systems.

"The reason for such metamorphoses is not some amazing spring phenomenon in which water takes on different colors, but industrial waste dumped into the city’s reservoirs," a local report said. 

No further details on the green waste were disclosed.