Iran’s aviation authority will not hand over to the manufacturer or to US authorities the flight recorders from the Ukraine International Airlines Boeing 737-800 that crashed moments after take-off from Tehran, killing all 176 passengers and crew.

Iran’s Civil Aviation Organisation head, Ali Abedzadeh, said that the information in the black boxes would be assessed in Iran under ICAO rules but Ukrainian officials could take part in the evaluation of the flight which had been destined for Kyiv on Wednesday.

This followed a reversal by the Ukrainian government in the immediate aftermath of the crash, when it ruled out an act of terror as a cause. Ukraine’s embassy in Tehran deleted a statement it had issued earlier in the day citing engine failure and replaced it with a new one saying “any statements about the reasons for the crash made before the commission’s decision are unofficial”.