This was the worst disaster since the Nedelin Catastrophe on 24 October 1964. A commission of military officers and chief designers reviewed the incident and requested changes to equipment and procedures, especially as regarded liquid oxygen handling. Another source reports that the explosion occurred during the fuelling of the Block E upper stage, and was due to hydrogen peroxide being present in a lox line filter and a confusion between fuel and lox lines. This error had always been possible, but had never happened in the 20 years of use of the booster before the explosion. The launch pad was badly damaged and not put back into service until April 1983.