A US official accused Moscow Thursday of preparing to plant fake evidence to make it look like the recent mass killing of Ukrainian prisoners in an attack on a Russian-controlled prison was caused by Ukraine. Kyiv and Moscow have traded blame over the strikes on the prison in Kremlin-controlled Olenivka in eastern Ukraine, which Russia said took place overnight on July 29. On Thursday the US official, who asked not to be named, said that intelligence reports show Russia will doctor the scene at the prison ahead of the possible visits by outside investigators. “We expect that Russian officials are planning to falsify evidence in order to attribute the attack on Olenivka Prison on 29 July to the Ukrainian Armed Forces,” the official told AFP, without sharing the evidence. “We anticipate that Russian officials will try to frame (Ukraine’s military)… in anticipation of journalists and potential investigators visiting the site of the attack,” the official said. More than 50 soldiers died in the incident, including troops who had surrendered after weeks of defending the Azovstal steel works in Mariupol. Russia has claimed that Ukraine carried out a strike on its own captured fighters, while Ukrainian authorities accuse Russia of covering up a deliberate massacre. Russian television images showed a charred room crammed with burned bed frames but independent experts are so far unclear on what could have caused the damage visible. The United Nations has announced a fact-finding mission, though it has not yet received final approval from Kyiv or Moscow. President Volodymyr Zelensky claimed there had been “a deliberate mass murder of Ukrainian prisoners of war.” Russia has carried out numerous attacks on civilians in its invasion of Ukraine, with evidence of summary executions and frequent aerial bombing or shelling of civilians. In each case, Moscow has either denied committing atrocities or blamed them on Ukraine attacking its own side. On Tuesday, Russian authorities said that Russian prisoners held by Ukraine had been subjected to “inhuman treatment.”