Emergency services were called to the building at Teralba in Newcastle last Thursday after reports of a fire.

Fire and Rescue NSW crews managed to extinguish the blaze but not before the building had been severely damaged.

Police found a body during an initial search of the townhouse but a second body was found later.

Two other people escaped the blaze.

Investigations were paused to assess the building’s structure but firefighters have since identified the cause.

A compromised battery went into “thermal runaway”, overheating and emitting toxic gases before exploding in flames, Fire and Rescue NSW said in a statement on Tuesday.

“The tragedies mark what FRNSW regards as the first deaths in NSW due to a lithium-ion battery-related fire,” the agency said.

Commissioner Jeremy Fewtrell said the fatal case appeared to confirm what firefighters had been “fearing for a while” after a rise in battery fires.

He warned the dangers of a battery going into thermal runaway were immediate, creating intense, volatile fires that were hard to put out.

Overheating batteries have already been linked to 44 fires in NSW in 2024 – a rate of about five per week – while 269 blazes were connected to batteries in 2023.

People are advised not to leave devices charging while they sleep, near flammable materials or exits to a home.

Police are working to identify the two people killed in the townhouse blaze after their bodies were recovered from the ruins.

-AAP