Thirty people required medical attention after being poisoned in a Russian swimming pool, as 250 times too much chlorine had been released into the water.
Most of those affected were taken to hospital including 21 children, following the incident in Astrakhan.
Six children are reportedly in intensive care, in a 'grave' condition and on oxygen support, according to Anastasia Krotova, spokesperson for the region's governor.
They suffered problems with breathing as well as eye issues.
According to reports, the incident occurred due to a mistake made by the staff responsible for cleaning the pool.
Reports claimed 250 times over the permissible limit of chlorine had been released into the water.
Emergency workers in hazmat suits were seen arriving at the pool, which has since been closed.
Video footage shows changing rooms left in a mess with clothes and towels strewn across the floor.
Another clip shows officials inspecting chlorine tanks inside a restricted area of the pool complex.
A criminal case has now been opened to investigate the circumstances surrounding the incident.
Astrakhan's regional Governor Igor Babushkin was also pictured visiting the Silishcheva Astrakhan Regional Children's Clinical Hospital to speak to families of those who had become ill.
Chlorine is used to keep pools clean and safe to swim in - killing harmful bacteria such as E coli and salmonella.
However, too much can lead to poisoning in humans, both when it comes into contact with skin and when gases released from the pool water are inhaled.
Symptoms of chlorine poisoning can include vomiting, nausea, a burning sensation, irritated eyes, difficulty breathing and chest pain.
Earlier this year, three people were killed in Moscow after a blogger dumped dry ice into a swimming pool at a party.
Popular blogger Ekaterina Didenko held a party for her 29th birthday in February, but the celebrations ended tragically when three people - including her 32-year-old husband Valentin Didenko died.
Natalia Monakova and Yuri Alferov, both 25, were declared dead at the scene.
According to reports, 25kg of dry ice was dropped into the pool to create a 'dramatic visual effect' to impress guests but as soon as the ice was poured people started to faint.
Featured Image Credit: East2West
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