Explosions were heard as a fire took hold in a carpark at Whangārei Hospital this afternoon.

A witness believes at least a dozen cars have been destroyed in the blaze in carpark 14, at the bottom of the hospital campus about 50m from any hospital buildings.

The man, who did not want to give his name, works at the hospital’s Child Health Centre which overlooks the carpark.

“We started hearing a few small explosions,” he said.

“There was lots of black smoke and probably, in total, at least a dozen vehicles destroyed.”

He had noticed the flames in a couple of cars just after 2pm on Tuesday and called Fire and Emergency on 111.

While his call wasn’t the first to 111, the fire spread from car to car before firefighters arrived.

The flames had been fanned by the steady wind, he said.

The man thought the fire probably started in just one car but spread along the row where the cars were packed in.

“It’s a very busy car park, it’s normally full during the day.”

The fire has since been extinguished.

The man said he felt sorry for those people whose cars were affected, especially his own colleagues.

Hospital workers have said the blaze was started by a car battery in an electric car. However, that hasn’t been officially confirmed yet.

A reporter at the scene said SUVs appeared to be among the vehicles burnt in the fire.

Some nearby houses were reportedly evacuated because of the risk of toxic smoke.

Whangārei Hospital remained open, according to Health New Zealand Te Tai Tokerau group director of operations Alex Pimm.

He said there are no reports of injuries and Health NZ is working with Fire and Emergency and police to ensure staff and patient safety.

Walkways and some nearby roads are cordoned off.

A nearby resident out walking down by the Raumanga stream was stopped by police who pulled out a rope, telling her she couldn’t go any further as it may be a crime scene.

Police have asked people to avoid the area while emergency services respond as well as for residents living nearby to close their windows.

Smoke can be seen over Whangārei Hospital. Photo / NZME

Resident Harmony Muller was on her way home with her daughter when she noticed thick, black smoke.

“ ... I was thinking, oh my gosh, I thought it was my house.”

Muller’s home is opposite the fire.

“We hope no one’s hurt,” she said.

While the drove of firefighters and police made Muller and her daughter feel safe, they had still found the blaze unsettling.

Emergency services at Whangārei Hospital where a fire ignited in a carpark. Photo / Brodie Stone