Ukraine's chief military prosecutor has ruled out a foreign sabotage plot in a massive fire at an ammunition depot that forced the evacuation of thousands of people.

The fire at the warehouse at a military base in Ukraine's central Vinnytsia region began late Tuesday and explosions at the site are continuing.

Anatoliy Matios, the country's chief military prosecutor, on Thursday denied earlier statements from authorities suggesting that a group of foreign saboteurs may have set the depot on fire. Matios said investigators were looking into possible negligence, abuse of power or sabotage by those who were authorized to handle the munitions.

Matios also said the investigators discovered that the fire alarm at the depot wasn't working and that its security force was understaffed.