Police will need to use DNA or dental records to formally identify a woman who burnt to death in a fiery high-speed car crash in Sydney's CBD over the weekend.

The woman died alongside brothers Steve and Jeff Nasr, aged 39 and 31, after the sports car they were in flipped and burst into flames in the early hours of Saturday morning.

Four days after the crash, a NSW police spokesman confirmed the woman's badly burnt body was yet to be formally identified.

Joseph "Joe" Bagala, 39, was the fourth person in the vehicle and the sole survivor, having been pulled from the burning vehicle by police.