BERLIN – A fire and a subsequent explosion at a former air-raid shelter in the northern German city of Hamburg where plant oils were being stored left 43 people injured on Tuesday, authorities said.

The city’s fire service said the fire broke out early in the morning in the six-story structure that dates back to World War II, news agency dpa reported. It wasn’t immediately clear what caused the blaze in the building, where around 100 tons of essential oils were stored and a carpentry workshop also was located.

The fire brigade evacuated more than 60 people from nearby residential buildings after being alerted to the blaze shortly before 4.30 a.m. Around 2 1/2 hours later, an explosion occurred as firefighters tried to extinguish the blaze.

The injuries ranged from smoke inhalation to suspected broken bones; 12 of the injured were firefighters and 19 people were taken to hospitals, the fire service said.

Authorities tried and failed to extinguish the fire by flooding the building with foam. Later Tuesday, firefighters with breathing equipment were sent in to tackle the blaze.