“A rechargeable lithium battery caught fire,” on-duty rescue service officer Håkan Månsson told TT newswire. “When these catch fire, they create a gas called hydrogen flouride, which you don’t want to breathe in.”

Hydrogen flouride easily and quickly penetrates the skin, damaging tissue and causing severe burns or skin ulcers. Breathing it in can damage the lungs, causing swelling and fluid accumulation, known as pulmonary edema.

“The seven people who have gone to hospital have probably been sent in because they’ve breathed it in, but I can’t say that for certain,” Månsson said.

According to police, one of the hospitalised individuals is a police officer sent in for assessment after breathing in smoke.

Police, ambulance and fire services were all dispatched to the scene following reports of an explosion just before lunchtime on Thursday.

“It’s a bicycle battery which has detonated and caused a fire,” police press spokesperson Filip Annas told the newswire.

The apartment has been destroyed in the fire with gas leaking into the stairwell, local newspaper Sydsvenskan reports.

“We believe this is an accident,” Annas told TT. “Looking at the information we have at the moment, there’s nothing which suggests that a crime has been committed.”