Massive explosions and a blaze at a military ammunition depot in central Ukraine forced authorities to evacuate over 30,000 people and close airspace over the region, officials said on Wednesday.

The Interior Ministry said in a statement Wednesday that firefighters were still putting out a blaze that broke out late Tuesday in the town of Kalynivka, 190 kilometers (120 miles) southwest of the capital, Kiev.

Authorities bused more than 30,000 people out of the area and turned off the electricity and gas supply, the Associated Press reported.

Four residential buildings were damaged by fire but no casualties have been reported.

Arriving in the region hours later, Prime Minister Volodymyr Groysman said "external factors" were behind the incident.

The cause of the fire is still under investigation.