A brewery leak in the Japanese port city of Nago has led to a shocking sight as the nearby seawater turned red, reports said.

Residents woke up Tuesday morning to find the water had turned a "gruesome" shade of red. The brewery, owned by Orion Breweries, claimed that the color change was caused by a coolant used to regulate the temperature of the equipment that had flowed into a nearby river.

Orion apologized for "the inconvenience and concern we have caused to nearby residents and other concerned parties."

"We believe it was caused by the leakage of propylene glycol – a food additive listed in enforcement regulations of the Food Sanitation Act – contained in cooling water used to cool our factory facilities," Orion Breweries said. 

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"We believe the leaked cooling water flowed into a river through a rain gutter, causing the sea to turn red," the statement explained.

The company managed to stop the leak by 9:30 a.m. local time and promised to prevent further leaks, The Japan Times reported.

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An unnamed local health official told The Okinawa Times that the government expected "no major impact on the environment" from the propylene glycol. 

The U.S. Agency for Toxic Substances and Disease Registry has determined propylene glycol as "generally recognized as safe" for use in food.

The city of Nago is well-known for its beach resorts and generally clear waters. The island of Okinawa, where Nago is located, drew 10 million tourists in 2019, according to Nikkei Asia.