Ukraine arms dump fire alarm 'was not working'
When one of Ukraine's biggest munitions depots exploded, prompting the evacuation of 28,000 people, officials blamed sabotage.
Now it has emerged that the fire alarm at the Kalynivka site in central Ukraine was out of action and the base was poorly protected.
Criminal negligence is being considered as a possible cause of the blasts, which injured two people.
Ukraine's president has warned of a threat to national security.
Security chief Oleksander Turchynov said the loss of munitions at Kalynivka, and in a similar incident in March at Balakliya in the north-east, was the biggest blow since the conflict with pro-Russian separatists began in 2014.
Criticising Ukraine's entire defence leadership, he warned that events at Kalynivka proved that Ukraine was incapable of protecting its strategic arsenals.
The exact cause of the accident at the missiles storage site in the Vinnytsia region is still unclear. Nearby homes were badly damaged as shells went off in all directions.
On Wednesday, Prime Minister Volodymyr Groysman said it was "no accident" that the Ukrainian army's arsenal had been destroyed and suspicion inevitably fell on pro-Russian separatists. Some reports suggested a drone may have flown over the site before the fire started.
But President Petro Poroshenko later told security heads that they had to learn how to protect strategic facilities from sabotage groups, but if there was another cause, those responsible had to be brought to justice.
Chief Military Prosecutor Anatoly Matios revealed that the fire alarms were out of action and that only half of the site's technical protection facilities were working, Interfax news agency reported.
There was also a problem with the military security guarding the base. Most of the officials there were elderly because wages were so low, he said.
The prosecutor said there were four theories as to what happened, ranging from criminal negligence involving workers at the military site to external sabotage involving an explosive device inserted into ammunition sent there for storage.