KYIV, Ukraine (AP) — The dramatic rupture of the dam that upheld Ukraine's largest reservoir released a torrent of water Tuesday, raising fears of widespread damage and flooding in areas where tens of thousands of people live.

It's not clear what caused the the breach in the Kakhovka dam, which was already damaged. Ukraine accused Russian forces of blowing up the facility, while Russian officials blamed Ukrainian military strikes.

The 30-meter-high (98-foot-high) dam and associated hydroelectric power station sit in Russian-controlled territory along the Dnieper River about 70 kilometers (44 miles) east of the city of Kherson — a flashpoint of Russia's war in Ukraine.

Together with the power station, the Soviet-era dam helps provide electricity, irrigation and drinking water to a wide swath of southern Ukraine, including the illegally annexed Crimean Peninsula.

The reservoir created by the dam holds some 18 million cubic meters (4.8 billion gallons) of water — a volume nearly equivalent to that of the Great Salt Lake in the United States. Those waters supply cooling systems at the Zaporizhzhia nuclear power plant, where fighting has repeatedly raised fears of catastrophic accident.

Russia has controlled the dam since the early days of the war. Last fall, the troops occupying it detonated explosives that damaged three sluice gates, which help regulate water levels when operated properly. Signs of damage to the gates were evident in late May.

Ukrainian officials and independent experts also say Russian forces have failed to maintain it, either deliberately or through neglect.

Earlier this year, water levels in the reservoir were so low that many across Ukraine and beyond feared a meltdown at the Russian-occupied Zaporizhzhia nuclear power plant. Since mid-February, the water level has steadily increased, according to data from Theia, a French geospatial analytical organization.

On Tuesday, Ukrainian authorities accused Russian forces of destroying the dam. Russia says military strikes in the contested area damaged the facility.

As floodwaters swelled, both Russian and Ukrainian authorities have ordered evacuations of towns and villages, though neither side reported any deaths. Officials said about 22,000 people live in areas at risk of flooding in Russian-controlled areas, while 16,000 live in the most critical zone in Ukrainian-held territory.

Ukraine’s Energy Ministry also said there is a risk of flooding at energy facilities in the Kherson region. Nearly 12,000 consumers in the city of Kherson have already been left without electricity, and there may be issues with water supply.

Upstream, meanwhile, riverbanks extended as water levels dropped. At the Zaporizhzhia plant, Europe's largest, the Ukrainian utility operator and the U.N. atomic energy agency said the situation was under control and there was no immediate risk to safety.

Ukrainian authorities warned about the possibility of an environmental disaster.

Mykhailo Podolyak, a senior adviser to President Volodymyr Zelenskyy, said “a global ecological disaster is playing out" and warned that "thousands of animals and ecosystems will be destroyed in the next few hours.”

___ Associated Press writer Lori Hinnant in Paris contributed to this report.