As reported by Censor.NET, this was said by Military Prosecutor of Sumy region Oleksii Liashenko on air of 112 Ukraine TV channel.
"The primary version is negligent practices by some officials during particularly dangerous works," Liashenko said.
He also informed that the minute examination of the scene to establish the causes of the accidental explosion of the AA missile was planned for today.
"As far as I know, the condition of the injured is stable," Liashenko added.
Earlier, three people were killed including a NATO representative in an explosion at a testing facility of Ukroboronprom State Concern. Two more persons with grave injuries were taken to the hospitals in Sumy and Shostka.