And the driver - who survived the crash - has posted an apology and photograph from his hospital bed.
Police say speed and alcohol were factors in the crash that happened at about 7.30pm yesterday.
The group were travelling in a Nissan Bluebird sedan, which was cut into two when it struck a power pole.
One of the victims was found in the vehicle's boot.
The 19-year-old driver survived the crash and is in Timaru Hospital.
He reportedly posted a photo of himself from his hospital bed to social media on Sunday with an apology.
"Hello everyone just wanted to say I'm not dead I am very very lucky to still be alive and I can't believe what has happened and I am so so so sorry to the families that I have put in pain coz of stupid mistakes that I made that has costed 5 lives," he said, according to Stuff.
The five victims were all local boys aged 15 and 16.
One of the boys' fathers learned of his death through a phone call last night.
"Oh my heart is broken my one and only... I just got the phone call that our son has passed away in a car accident tonight," he posted on social media.
The Herald has reached out to the man for comment.
An uncle of the teen also paid tribute.
"Life is so precious - especially this one, our boy, our sweet boy," he said.
"He has that cheeky attitude and grin like his father, that presence and calm poise like his mother.
"My nephew , I love you."
The Herald has spoken to a number of their friends and family today.
Their names will not be published yet.
A cousin of a 15-year-old victim visited the scene of the crash soon after she heard the news.
"I really am in shock," she said.
"You don't believe it until you see it. I don't believe he's gone.
"He's just a young, sweet kid ... he doesn't need this."
She said her cousin was "a cool kid" and she was struggling to come to terms with his loss.
"It doesn't make sense to me," she said.
"I just don't get it."
She took a piece of the car's wreckage from the scene as a memento.
A friend of the same victim said he went to the site for some "peace of mind and see what happened".
He said it was important people got the message to be safe on the roads.
He said his mate was "still young, still growing up" and described him as having "a lot of cheekiness in him".
"He always knew how to make you smile, make you laugh. Every time he walked in, he'd just brighten the room up," the friend said.
"I'm going to miss him a lot."
A friend of two other victims also paid tribute.
She said one of the youths "always smiled and had lots of friends".
Another was "a funny guy".
"He always knew how to make people laugh," she said.
"The last time I saw him was 24 hours before the crash on Friday.
"I'd always see him walking around the town with his mates. [He] was loud at times but generally a great guy to be around. He was friendly and loved an adventure.
"All his friends loved him and we will never forget him."
Police said the immediate families of all five boys had been informed, but their names would not be released formally until wider whānau had been reached.
Police are investigating the crash.
"To have five lives lost in an instant is a terrible tragedy, and our thoughts are with their families," said Superintendent Steve Greally, of the National Road Policing Centre.
Aoraki Area Commander Inspector Dave Gaskin said his thoughts and prayers were with the family of the young men.
"They woke up today to a nightmare that won't go away," he said.
"Timaru's a very small community ... It is a tragedy and it will reverberate around our community for a long time."
Police are yet to speak to the driver.
