MOSCOW — Ukraine’s chief military prosecutor on Thursday 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, setting off a series of explosions and prompting the evacuation of 30,000 people. Electricity and gas supplies were cut off in the area, and trains were severely delayed across the country. The fire was still blazing Thursday.

Local media reported that about 188,000 tons of munitions were kept at the depot in the town of Kalynivka, 190 kilometers (120 miles) southwest of the capital, Kiev, including rockets for the Grad multiple grenade launchers.

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 investigators discovered that the fire alarm at the depot wasn’t working and that its security force was understaffed.

“Neither the investigators, nor the Security Service, nor any law enforcement agencies found any groups of saboteurs in the Vinnytsia region that people are talking about on Facebook,” Matios said, an apparent reference to comments made by several senior Ukrainian officials on social media Wednesday blaming Russian saboteurs for the fire.

Authorities launched checks at military bases across the country in the aftermath of the fire and discovered serious violations. Prosecutors found two “completely drunk” colonel and lieutenant colonel in charge of security at a military depot holding Soviet-era ballistic missiles.

“I think such cases are not unique,” Matios said on Thursday, quoted by the Interfax news agency.

In Kalynivka, firefighters on Thursday morning were still unable to put out the blaze because there were still periodic explosions at the site, said Mykola Chechotkin, chief of the Ukrainian State Service for Emergency Situations.

“Explosions are still happening as you can hear,” he told reporters in Kalynivka. “It’s too dangerous for firefighters to access the area even though four fire tanks are working there.”