Water experts have been called in to investigate after a lake suddenly turned a bright shade of pink.
Local residents in the town of Nizhyn in northern Ukraine's Chernihiv Oblast region raised the alarm about the spectacular colour change.
They posted photographs on social media of the Nizhyn Lake overgrown with weeds showing the water had turned pink.
They fear it has been contaminated with chemicals and report that there is also a strange odour coming from the lake.
However, they add that the smell has been noticeable for about a year while the water has only just changed colour.
Local resident Vadym Shekera commented: "I have been living here for 15 years and I've never seen anything like that before."
But he added that he was hopeful that it was not a serious pollution incident as he had not seen any dead fish floating on the surface.
Local officials said that they were concerned about the situation and had sent an expert team to investigate.
They will be testing the water to find out the reason for the sudden colour change.
Spokesman Genadiy Chernyshov said: "We are concerned about the situation. A group of experts was sent to the lake to investigate it.
"The water will be examined by three different organisations. If some dangerous chemicals are found, the necessary measures will be taken."