An early morning explosion in central Turkey has killed four workers at an ammunition depot.

The Anatolia news agency said the blast Monday caused a large fire at a military-owned building in the town of Yahsihan.

A local official says an investigation into the Kirikkale province blast is under way.

A 1997 explosion at a state-run weapons plant caused an evacuation of Kirikkale. That explosion caused an enormous fire that took days to extinguish.