Investigators searching the site where a Russian military transport plane crashed in a border region near Ukraine reportedly have found the plane’s flight recorders, a day after Moscow accused Kyiv of shooting down the aircraft and Ukraine’s president demanded an international investigation.

The Il-76 fell from the sky and crashed in a huge ball of flame in a rural area of Russia on Wednesday, killing all 74 people on board, Russian authorities said, as the war nears its two-year mark.

Russian officials accused Kyiv of shooting down the plane with two missiles, claiming that 65 Ukrainian prisoners of war were on board as they headed for a prisoner swap. They offered no evidence for their claim.

Ukrainian authorities confirmed a prisoner exchange was due to happen Wednesday, and that it was called off, but said they had no information about who was on the plane.

Kyiv officials gave no direct response to the Russian claim that Ukraine struck with plane with a missile, though they noted that Russian aircraft were legitimate targets and that Moscow had requested no safe passage in the context of the prisoner swap. They cautioned against spreading unverified reports.

Kremlin spokesman Dmitry Peskov on Thursday repeated the allegation that Ukraine had downed the plane, describing it as “a totally monstrous act.”

Ukrainian President Volodymyr Zelenskyy didn’t directly address Moscow’s allegation but said Ukraine would push for an international investigation.

“It is necessary to establish all the facts, as much as possible, considering that the plane crash occurred on Russian territory — beyond our control,” he said in his nightly video address late Wednesday.

“It’s obvious Russians are playing with lives of Ukrainian POWs, with the feelings of their relatives and the emotions of our society,” Zelenskyy said.

Russian Foreign Minister Sergey Lavrov called for an emergency meeting of the U.N. Security Council, which was expected to take place on Thursday afternoon in New York.

The discovery of the plane’s flight recorders was reported by the state-owned RIA Novosti news agency, citing emergency services.

However, there was little hope that the true circumstances of the crash and the Russian allegations would be clarified by the investigation.

Deadly incidents followed by claims and counterclaims are a feature of the war, used as ammunition to tarnish reputations and swing public opinion.

The 1,500-kilometer (930-mile) front line has been largely static amid a second winter of fighting. As both sides seek to replenish their weapons stockpiles, the war recently has focused on long-range strikes.