The person who stole a woman's wallet and phone whilst she was being treated for serious injuries after a crash is callous and added to her trauma, police say.

Photo: Facebook

The crash happened shortly after 1pm on Thursday on Cosgrove Road in the Auckland suburb of Papakura.

Inspector Tony Wakelin said a 39-year-old woman who was seriously injured in the crash was removed from her car and taken to another vehicle to await medical attention.

"It has been subsequently established that whilst she was receiving medical attention a person or persons has removed her wallet and phone from her car. A credit card from the wallet was fraudulently used on eight occasions later that day."

Mr Wakelin said police were following strong lines of inquiry and investigating CCTV footage.

"It's cowardly and callous, it really is. It shows the two extremes of people in this society.

"The majority of them on that day were there to look after the victim, make sure she's cared for in a traumatic situation. Then we have these low-lifes that have come along and taken property, taking advantage of the bag being unattended, and stolen property and then gone on and caused more trauma to her by using it," he told Checkpoint.

Murray Howell posted on social media, saying his partner Shevaughn Johnstone, the victim in the crash, was doing well.

"She had to be cut out of the vehicle in a very serious condition with major damage to her right arm, and has no memory at all of the events leading up to or afterwards.

"During this horrible accident a low-life piece of scum along with a couple of his associates took their opportunity to go into Shevaughn's hand bag, while she was being cut out of the vehicle and attended to and stealing, yes STEALING her iPhone 6 and her wallet," Mr Howell said.

He said he found the whole thing beyond belief.

"These people then proceeded directly to Z Kingsway and made their first Pay Wave purchase for $23.90 to test that card before going on a shopping spree."

He said the card was then used at Z Papakura North, The Warehouse Takanini and Grove Service Station until there was no money left.

"You sons of a bi*** were spending her money before she even made it to the hospital!!!!!"

Mr Howell said he was able to track her phone to a hedge opposite the Z Service Station on Clevedon Road.

"If I had lost that phone and lost Shevaughn that day you would have stolen more from us than you could ever comprehend - The sentimental value of the messages, photos to us are priceless and you took them from her when your human instinct if you had any should have been one of help - How can you justify such an action!"

-RNZ