The United Nations has said that Russian accounts of a rocket attack on a camp holding Ukrainian prisoners of war in July 2022 are not supported by the evidence.

More than 50 Ukrainian prisoners were killed in the strike that year on a detention center in the town of Olenivka. An extensive CNN investigation published in August last year demonstrated that the Russian narrative that the camp had been hit by a Ukrainian HIMARS rocket did not stand up to scrutiny -- a finding now supported by the findings by the UN Human Rights Commissioner (OHCHR).

Russian and local officials from the self-declared Donetsk People's Republic said the attack was carried out by the Ukrainian side, using one of the HIMARS rockets that had been recently supplied by the US.

The morning after the blast, Andrey Lazarev, who works for the Russian Defense Ministry's Zvezda media channel, pointed to fragments, one of which included the serial number of a HIMARS rocket in remarkably good condition.

Russian Defense Ministry spokesman Major General Igor Konashenkov said the detention center was "hit by a missile attack from the American HIMARS."

But CNN's investigation, based on analysis of video and photographs from the scene, satellite imagery from before and after the attack and the work of forensic and weapons experts, concluded that "the Russian version of events is very likely a fabrication. There is almost no chance that a HIMARS rocket caused the damage to the warehouse where the prisoners were being held."

Experts consulted by CNN discounted a HIMARS strike on Olenivka -- but could not say definitively what killed and wounded so many prisoners. The investigation noted that "experts say most signs point to an intense fire, and according to several witnesses there was no sound of an incoming rocket."

'A right to truth, justice and reparations'

A UN statement issued Tuesday concurred that "the information available and our analysis enable the Office to conclude that [the strike] was not caused by a HIMARS rocket."

"The Russian Federation provided neither satisfactory assurances about secure access for the United Nations to visit the particular site, nor granted general requests by the UN Human Rights Office to access areas of Ukraine under the temporary military control of the Russian Federation."

The OHCHR said that it had been able to "conduct extensive interviews with survivors of the incident at Olenivka and undertaken detailed analysis of available additional information...While the precise circumstances of the incident on the night of 28-29 July 2022 remain unclear, the information available and our analysis enable the Office to conclude that it was not caused by a HIMARS rocket."

The OHCHR added that "based on the information available, it is not possible at this stage to establish either the specific source of the explosion, nor the exact direction from which a weapon may have been fired."

Survivors and families of the injured prisoners "deserve the truth to be known, and for those responsible for breaches of international law to be held accountable," UN Human Rights Chief Volker Türk said Tuesday.

"Our office has met with the families of the victims and heard their pleas for truth and justice -- and indeed, they have a right to truth, justice and reparations. For all those impacted by this tragedy, we must do all we can to ensure justice is done."