At least 38 people were injured in a fire and explosion in a World War II-era bunker in Hamburg, Germany.

Firefighters used foam to douse the blaze, and prevent the ignition of about 100 tonnes of essential oils stored in a carpentry workshop inside the bunker.

• Fire crews continue to battle Sydney factory blaze
• Hundreds evacuated in dangerous California blaze
• NSW bushfire ‘suspicious’

Firefighters are decontaminated. Photo: AAP

Several firefighters who rushed to the pre-dawn blaze were injured by the force of a blast strong enough to hurl debris and bicycles through the air.

“For now, we won’t send anyone else into the building because the situation is unclear,” a fire brigade spokesman told national news agency DPA.

“We plan to flood the bunker with foam to extinguish the fire.”

Twelve firefighters were among the 38 people injured, who also included nearby residents who suffered smoke inhalation.

Officials said they were investigating the cause of the blaze in the concrete bunker in a residential area of the harbour district of Rothenburgsort.

Hundreds of Nazi-era bunkers remain scattered across German cities, where they were often the only buildings to survive Allied bombing raids that destroyed surrounding neighbourhoods.

With their thick concrete walls, many above-ground bunkers proved too difficult to safely demolish after the war and city authorities opted to keep many of them to house businesses or as venues for cultural activities.