"Man Cavers" around the country have united for Ashburton dad Jason Alexander, offering money, accommodation, and beer as he flew from Christchurch to Auckland to be with his critically injured daughter in hospital.

Sunmara Alexander, 15, is fighting for her life in Auckland Hospital after suffering extensive burns in the same crash that killed her 17-year-old sister, Tayla Alexander. 

The girls' car careered down a bank in Christchurch's Port Hills on 27 November, about 11pm, and burst into flames. Two other teenagers were injured in the crash.

A GoFundMe page set up on Monday for their father, by members of online community The Man Cave, raised $3000 within its first 24 hours.

Jason Alexander posted about his plight on the group's closed Facebook page – seeking advice for his trip to Auckland, said Peter McDonald, also member of the group.

McDonald, a father of three from Katikati, said the grieving dad's situation "really struck a chord" with many "Man Cavers".

We're brothers and brothers look out for each other

"As soon as he posted, hundreds and hundreds of comments appeared. People were offering him a free place to stay, beers, advice, a lot of condolences ... it was amazing."

An admin for The Man Cave started the GoFundMe, said McDonald.

The page's blurb said that as Jason Alexander was enduring "grief and heartache that no parent should ever have to feel", "the legends and GCs [good c....] of the The Man Cave will pull together and help him financially as much as we can".

Comments on the GoFundMe spoke of "bros" and "cavers" banding together in times of need.

"We're brothers and brothers look out for each other," read one.

"One GC to another in the spirt of [The Man Cave]. Am so sorry for your loss. We're here for you when you need us."

"Brother, I got no words," read another.

"I just wish you love and courage and strength as you go through this nightmare."

McDonald said the group mainly shared images of fast cars, humorous memes, and women in risque poses – but was also "a good place to get anything off your chest" and find support.

Sunmara Alexander was due to have surgery on Monday night and could be in a coma for months, Jason Alexander told Stuff previously.

He described his daughter as a "complete practical joker".

Jason Alexander was booked to fly back to Ashburton on Tuesday. Tayla Alexander's funeral is due to be held on Thursday.

Tayla was the "mother hen" of the family and "always put others first before herself", Jason Alexander has said.