Worksafe and Auckland Transport are investigating the incident where a woman died after falling down double-decker bus stairs in Silverdale, Auckland.

A woman who died after falling down the stairs of an Auckland double decker bus was an "amazing woman who will be missed dearly by all", her death notice says.

She was Coreen Johns, 74, of Orewa. Her funeral will be held in Auckland on Wednesday.

Johns was taken to hospital after she fell down some stairs on a Northern Express bus service, run by Ritchies Transport, in Silverdale, near Orewa, about 10.30am, Friday. She died that evening in hospital.

Police Senior Sergeant Nick Herd said Johns found a wallet left behind by a previous passenger and had gone downstairs to give it to the driver.

"It is at this time that she has fallen," Herd said.

The death was an "absolute tragedy for this woman's family and our deepest sympathies are with them during this difficult time".

The matter was referred to the Coroner.

A death notice published in the New Zealand Herald said Johns was an "amazing woman who will be missed dearly by all".

Her family declined to comment when contacted by Stuff.

RITCHIES The woman died going down stairs when she was trying to return a wallet.

Kelly Clark was one of three people on the bus who rushed to Johns' aid after hearing a "big bang".

Clark, who was sitting at the front of the bus on the top level, went to see what had happened and saw Johns on the stairs.

"We just got someone to ring an ambulance straight away and moved her down the stairs a little," Clark said.

"Her legs were up the stairs, she looked in a really awkward position and I wanted to get her on her side because she was on her back. I know you need to get them in the recovery position."

Clark said the 74-year-old was never responsive at any stage but was still breathing.

She noticed a large lump on her head and assumed she had internal injuries.

Hearing that Johns had passed away from the accident, Clark said she was surprised but knew her injuries were serious.

Clark said the bus was sitting in the Hibiscus Coast Park n Ride when the accident happened.

"I don't think the bus was even moving, I think we had only just released the brake."

Clark said she managed to find a contact number for Johns' son in her bag and he arrived at the scene shortly before the ambulance.

"He told us she had recently had a heart attack and we actually found her heart attack spray," Clark said.

She said the bus driver didn't seem to know what to do in the situation.

Auckland Transport (AT) spokesman Mark Hannan said Ritchies was undertaking a full investigation into the incident

"AT will assist in that, and any other inquiries or investigations in any way it can," Hannan said.

"Our deepest condolences go out to family and friends affected by this tragedy."

Worksafe confirmed via Twitter it was also making inquiries into the incident, though its post had a different date for the incident.

We have been advised that a passenger on a double decker bus in Silverdale has died after falling down the stairs of the bus yesterday. We are making initial inquiries. pic.twitter.com/lCTdQQl3VI — WorkSafe New Zealand (@WorkSafeNZ) July 9, 2018

Ritchies Transport's fleet had 260 buses, 19.08 per cent of buses in Auckland, but its buses accounted for 48.07 per cent of bus accidents between 2015 and 2017 according to figures released by First Union in May. Ritchies disputed the data.

Bus drivers at the company went on strike in May over pay and conditions.

Workers were being paid "bottom dollar" at the time according to comments from First Union organiser Graham McKean.

"Many of these employees have been driving for decades and they have the responsibility of the wellbeing of hundreds of people a day on their shoulders. Pay them what they're worth," he said at the time.

In April the company lodged a request to hire 110 migrant workers to drive buses citing a shortage of bus drivers in New Zealand.

AUCKLAND'S DOUBLE DECKER BUS FLEET

Hannan said there were 91 double-decker buses across Auckland.

They carry up to 100 passengers - significantly more than their single-levelled counterparts which can carry 45 to 70 passengers.

They are used across the east, central Auckland and the North Shore networks.

Double-decker buses are generally 4.25 metres tall and 2.9 metres wide.