A teenager has died and another is fighting for life after their car slammed into a tree at Para Hills, moments after being chased by Police.

Hayden Pepe was allegedly behind the wheel of the silver Ford Sedan that crashed into a creek bed off Nelson Rd, two minutes after Police tried to stop the vehicle around 10.30 last night.

The 18-year-old sustained critical head injuries and was rushed to hospital, his passenger and friend 19-year-old Philip Frith died at the scene.

A teenager driver remains in a serious condition in hospital and his teenage passenger was killed in a high-speed crash in Adelaide. (9NEWS)

Mr Frith's devastated girlfriend was among those to visit the scene today.

His friends say the young man, who worked as a panel beater in Salisbury, was well liked.

"He was just a really awesome person, very relaxed and really kind a, it’s just horrible it’s taken such a young precious life away," friend Stephanie Swarbrick said.

"It's heartbreaking, it really is heartbreaking that this has happened."

South Australian police pursued the Ford Sedan for some time before calling off the chase in Para Hills, in the city's north. (9NEWS)

"He really got along with everyone, to be honest, I don't honestly see what's happened here," friend Ben Ford added.

Police say a patrol tried to stop the car after it was allegedly spotted speeding on Nelson Rd.

"The initial advice I am getting, it's greater than 100 km/h... bearing in mind it's a 60 km/h zone," Assistant Commissioner Paul Dickson said.

A short time later, the teenage driver lost control of the car and crashed it into a group of trees, before a creek bed. (9NEWS)

SA Police has launched a major investigation into the crash and the chase but say the officers involved terminated the pursuit before the crash.

“They stopped, went back to the normal speed of the vicinity and they turned their lights and sirens off and then sometime later they came across the vehicle,” the Assistant Commissioner added.

"There's no evidence to suggest they haven't complied with our Policy."

The 18-year-old driver was rushed to the Royal Adelaide Hospital, however his 19-year-old passenger died at the scene. (9NEWS)

Police want to speak with anyone that might have dash cam video that shows the silver Ford sedan travelling in the area last night.

Investigators say if the driver recovers, he will likely face serious charges.