TRIKALA, Greece (AP) — An explosion and fire at a cookie factory in central Greece killed five female night shift workers and left seven injured, authorities said Monday.

The injured, including a firefighter, were hospitalized after the blast at the Violanta biscuit plant near the city of Trikala, about 320 kilometers (200 miles) north of Athens.

The blast occurred during the night shift, and the resulting fire gutted the plant. Fire crews battled the blaze for hours before recovering four bodies — all women — from the destroyed building. Parts of a fifth female body were later recovered, and were to be formally identified using DNA tests, fire officials said.

“Unfortunately, the day began in the shadow of the tragic accident in Trikala, at a modern food production facility,” Prime Minister Kyriakos Mitsotakis said in a televised address at a Cabinet meeting. “Our thoughts today are with the families of the victims. On behalf of the entire Cabinet, I express to them our deepest condolences.”

Violanta, a locally-based business, has national distribution for a range of products, including wholewheat cookies, chocolate‑sandwich biscuits and cereal bars.

Police said investigators suspect the explosion may have originated near the ovens, which operate around the clock. Six workers and one firefighter were being treated at a hospital in Trikala, none in serious condition.