Young woman and man killed in car crash after 21st birthday party

A young man and woman who died after their car slammed into a power pole in Deception Bay, north of Brisbane, had just left the man's 21st birthday party.

Witnesses reported hearing the crash about 3.30am on Park Road and some rushed out of their homes to help.

A local nurse and another woman were the first on the scene but found there was very little they could do. 

The driver, Sarah Mitchell and her boyfriend Jordan Whittle, both died at the scene, police said.

Friends say the pair had been drinking nearby at Whittle's 21st birthday party and had argued before getting in the car.

Their car was mangled and wrapped around the pole, and its engine lay about 30m away.

The speed limit where the crash occurred is 60km/h although drivers are advised to only go 50km/h.

Residents told 9NEWS even that is too fast to navigate the bend.

Police said they believe the car was the only vehicle involved in the crash, and are continuing to investigate.