KYIV, Ukraine (AP) — Ukraine on Tuesday accused Russian forces of blowing up a major dam and hydroelectric power station in a part of southern Ukraine that Russia controls, sending water gushing from the breached facility and threatening possible massive flooding and what officials called an “ecological disaster.” Ukrainian authorities ordered hundreds of thousands of residents downriver to evacuate. Russian officials countered that the Kakhovka dam was damaged by Ukrainian military strikes in the contested area. Ukrainian authorities have previously warned that the failure of the Kakhovka dam could unleash 18 million cubic meters (4.8 billion gallons) of water and flood Kherson and dozens of other areas downriver.