CNN — Beaches in the southern Ukrainian region of Odesa have been closed off after filthy waters from a collapsed dam washed downstream, posing a “genuine threat” to local residents, authorities say.

The toll from the collapse of the Russia-controlled Nova Kakhovka dam on June 6 has risen to 45, with both sides giving updates on those killed.

The collapse destroyed villages, flooded farmland and cut off power and clean water supplies to tens of thousands of people .

Floodwaters are receding, but debris washed down the Dnipro river – which flows into the Black Sea – turning Odesa’s coastline into “a garbage dump and animal cemetery,” according to Ukrainian authorities.

“The beaches of Odesa have been declared unsuitable for swimming due to a significant aggravation in the condition of water in open water areas (sea, estuary) and a genuine threat to the health of the city residents,” the Odesa municipality said in a Telegram post Sunday.

Odesa’s stretch of sandy beaches and holiday resorts were once popular with Ukrainian and foreign holidaymakers before Russia’s invasion.

The beaches have been largely abandoned by swimmers in recent months as mines continue to wash on the shoreline.

Authorities raised the alarm about the declining water quality, in a Telegram post on Saturday, saying that lab tests had “identified infectious agents over the past week.”

Traces of salmonella, worm’s eggs and worm’s larvae were all found in the water which also “significantly” exceeded permitted levels of E. Coli.

“The presence of all of these biological pathogens in the water of open water areas in Odesa region, including the Black Sea, the Bilhorod-Dnistrovskyi Estuary, and the Danube River, constitutes a genuine threat to the life and health of the population,” the municipality added.

• 'It's a nightmare': Burst dam triggers emergency in Ukraine
• Ukraine’s dam collapse is both a fast-moving disaster and a slow-moving ecological catastrophe
• 'They should not be forgiven': Angry residents flee flood stricken Kherson after attack

Authorities announced that Odesa residents were also prohibited from selling fish and seafood “unidentified places of fishing” near markets and shopping centers.

It remains unclear if the Nova Kakhovka dam was deliberately targeted or whether structural failure was behind its collapse.

Homes are seen underwater in a flooded neighborhood in Kherson, Ukraine, Wednesday, June 7, 2023. Felipe Dana/AP

Kyiv says Russia blew up the dam “in panic” ahead of a planned Ukraine counter-offensive, while Russia accuses Ukraine of launching “mass artillery attacks” on the structure to deprive Crimea of water and provide a distraction from the battlefield.

At least 16 people are dead and 31 are missing in flooding from the collapse, Ukraine’s Ministry of Internal Affairs said Saturday.

It added that 3,614 people had been evacuated from the flooded areas “including 474 children and 80 people with reduced mobility.”

In a Telegram post the same day, Andrey Alekseenko, the Russian-backed head of the government of the Kherson region, said 29 people had died in Russian-controlled territory.

Local volunteers prepare food for people affected by floods in Kherson on June 11. Celestino Arce/NurPhoto/Reuters

The area surrounding the dam has been one of the most heavily contested regions since Russia launched its full-scale invasion of Ukraine in February 2022.

The city of Kherson, which sits on the west bank of the Dnipro river, was liberated by the Ukrainian military in November after eight months of Russian occupation.

But much of the east bank of the river south of the Nova Kakhovka dam remains under Russian control.

The reservoir supplies water to large swaths of southern Ukraine, including to the Crimean peninsula which Russia illegally annexed in 2014.