Members of the public rushed to help after a Ford Ranger ute collided with a Toyota HiAce van on the Stuart Highway 75km east of Darwin about 12.50pm on Wednesday.
But the intense fire engulfing the vehicles prevented would-be rescuers approaching.
Their bravery was highlighted by Northern Territory Police, who said they did everything they could to save lives.
"Unfortunately, despite the efforts of everyone involved ... five lives were lost," Acting Commander Richard Griffiths said on Thursday.
The charred remains of the crash were still visible on Thursday as police investigated, setting up canopies and a black screen fence at the scene amid burned-over eucalypt woodland.
From outside the police cordon, dark mangled wreckage that hardly resembled vehicles could be seen on the road.
A truck with its tray down waited nearby as it was prepared to take the burnt vehicles away.
A detour of about 2km was in place for one-way traffic on Thursday afternoon.
Police said witnesses had told investigators the Ford Ranger was travelling "at excessive speed" and overtaking dangerously in the minutes leading up to the collision.
The driver and three occupants in the Ranger died in the crash - two men and two women aged from 23 to 36.
The sole occupant of the Toyota - a 69-year-old woman - also died.
The NT Disaster Victim Identification Team was at work ensuring all the deceased were identified and families kept informed respectfully, police said.
Names of the dead had not been released but police believe they know the families involved and had contacted them, Commander Griffiths said.
The victims were from the Roper Gulf and the Greater Darwin regions, but police gave no further details of their identity.Â
The tragedy would have a "long and deep impact" on all concerned, including family, friends and first responders, Commander Griffiths said.
Anyone with information about the crash should contact police, he said.
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