New Zealand Professional Firefighters Union vice-president Martin Campbell earlier said this was another example of an ageing and poorly-maintained fleet, and the consequences could have been serious.

Fire and Emergency New Zealand said staff safety was “of prime importance”. While the agency had been unable to replicate the fault yet in testing, the truck would remain out of action until the issue was fixed.

Fire and Emergency crews were called to the large fire at the recycling plant on Hillside Rd in Wairau Valley at 5.24pm yesterday.

Witnesses reported seeing multiple fire trucks rushing to the scene, with toxic smoke visible across the city.

Bronwyn Patterson, who lives two streets from the blaze, told the Herald “things went boom, with projectiles going into the air”.

This morning Campbell told the Herald part of the emergency response went badly awry when one of the aerial units malfunctioned with two firefighters in the basket above the flames.

“It’s sort of semi computer-operated, the operators will tell a computer where to send the aerial basket to. For whatever reason, that computer shut down and stopped working,” he said.

The usual steps of turning it off and on again and other troubleshooting failed to work, and emergency back-up procedures failed, he said.

“One of the emergency manual levers actually broke off in a firefighter’s hand,” he said, which had been the “last resort” to bring the basket down.

New footage provided to the Herald reveals the serious position the crew found themselves in.

A witness, who took the video, said he had seen an aerial basket surrounded by smoke.

“We could hear the explosions constantly going off which sounded like gunshots,” he said.

“At this stage we could only see the lone fire unit, they were sitting motionless, and no hose or water were being used as the explosions went off and smoke clouds engulfed them.

“At this point I was getting concerned for them as the fire appeared to be right on them and the flashes or flames were bursting in the background of their silhouette. My son even mentioned the explosions and burning structure of the building reminded him of the great Chicago fire.”

He said another fire truck nearby began using its hose, at which point he saw the stranded unit appear to descend.

“It was a relief seeing this unit activated and putting the fire [out] and getting some sense of control, and also seeing the stranded unit lowered. We left soon after.”

Campbell confirmed the footage showed the trapped firefighters.

“It’s an incredibly scary situation,” he said this afternoon.

“Firefighters always want to have an escape route in mind … [the incident] has left those firefighters with no escape route. That’s a worst-case scenario, to be trapped in that position.”

He said the crew were both veteran firefighters.

“That video footage is probably taken at or very close to the time that it broke down.”

He said the smoke was “very black, it’s very toxic”.

“You literally can’t see a hand in front of your face. It’s like having your eyes shut.

“Yes, we do have the air tanks that will give us a limited amount of time to stay alive. The air tanks and the uniform will only protect us so much.”

Campbell said being above the fire was “the worst place to be” because all of the heat rose.

“You’re immediately above the hottest part of the fire. I would imagine it would be like being above a mini-volcano about to erupt.”

Campbell said the malfunction was a symptom of an ageing, poorly-maintained fleet of fire trucks, and the union would be sending out advice to its members not to use the truck in question until a thorough investigation had been completed and the fault was fully fixed.

Fire and Emergency region commander Ron Devlin confirmed in a statement the aerial component of the appliance had faulted “and was unable to be moved while operating at the fire”.

“The two-person crew was removed to safety from the platform cage by another similar appliance that was on scene,” he said.

“An aerial appliance from Hamilton was brought through, however this was not required at the fire, and it stood by at Auckland central fire station, returning to Hamilton later in the evening.

“The appliance is now at the workshops for cleaning and testing and at this time we have been informed that they have not been able replicate the fault that occurred during the fire.”

He said the safety and wellbeing of staff were “of prime importance”.

“A full investigation will be carried out into the appliance incident and the appliance will remain off the run until we have remedied the fault and it is tested to be fully operational.”

Firefighters were still on the scene of the blaze this morning working to fully extinguish the fire.

Assistant commander James Hall said three fire trucks and two ladder trucks were working with two diggers to open up the badly damaged structure.

“While there are small flare-ups, there is no significant smoke and the lithium-ion batteries involved in the fire are no longer a hazard.”

It’s believed the batteries may have caused the fire.

“The emergency message alert advising people to stay inside was lifted during the night.”

He said an investigation was under way into the cause of the fire and crews were expected to remain on the scene until later this afternoon.

Melissa Nightingale is a Wellington-based reporter who covers crime, justice, and news in the capital. She joined the Herald in 2016 and has worked as a journalist for 10 years.