A fire that completely gutted a Christchurch townhouse was caused by a charging e-scooter that exploded, Fire and Emergency (Fenz) have confirmed.

The blaze was reported to Fenz shortly before 10pm on February 27, on New Brighton Rd, opposite The Palms shopping centre in the suburb of Shirley.

Fenz’s investigation into the cause of the fire which was completed on Wednesday, determined the fire was accidentally caused after an e-scooter that was charging went into thermal runaway and exploded.

Thermal runaway is an uncontrollable increase in temperature, which often results in system failure. It often occurs in electrical circuits, chemical reactions and battery cells.

Both levels of the property were extensively damaged, with all household items reduced to charred remains. Photo / Pierre Nixon

A Fire and Emergency spokesperson said they’re reminding the public that it is important to take care when using these batteries as they are a fire risk when not stored, charged, used, or disposed of correctly.

“Only use chargers that are supplied with the device, don’t charge them on or near flammable surfaces, and avoid leaving lithium-ion batteries or devices charging for prolonged periods of time,” the spokesperson said.

The spokesperson referred to further lithium-ion battery safety information which can be found here.

A neighbour, two doors down from the property, earlier told the Herald he heard a large boom and what sounded like an earthquake.

“My partner said, ‘It’s an earthquake, it’s an earthquake,’ and we could definitely smell the smoke,” he said.

“It was a violent fire and was moving very quickly.”

The man said when he noticed it was a fire, his partner tried to collect valuables, including her passport.

“We evacuated as soon as we could.

“The fire brigade was here very quickly, and so was St John.”

Fire crews battled the "well-involved" fire at an apartment in the Christchurch suburb of Shirley. Photo / George Heard

The man told the Herald a young child was rescued from the top of the property’s window and he thought it might have been one of the parents and a bystander who saved the child from the blaze.

“Whoever it was, they are a hero, as they couldn’t go down because the fire was raging,” he said.

The neighbour said he didn’t know the residents who lived in the property as they had moved in recently.

Hato Hone St John earlier said it was advised of the fire at 9.54pm and dispatched two ambulances, a rapid response vehicle and an operations manager to the scene.

A neighbour said a young child was rescued from the top of the property’s window. Photo / George Heard

It treated three patients, one with serious injuries and two with moderate injuries.

Another witness, who asked not to be named, earlier told the Herald they heard a loud bang before plumes of smoke erupted from the apartment block.

They said they saw a mother and child on the top floor of the building.

“The mum passed the child out the top window and two boys from the street were underneath and caught her,” they said.

Afterwards, the mother climbed through the top window and dropped to the ground, said the witness.