A woman killed in a hit-and-run in inner Brisbane over the weekend may have been lying on the road, or on her hands and knees when she was struck, police say.

Ashleigh Humphrys died early Sunday morning after spending the night out with friends celebrating her 20th birthday.

Police said she was hit while walking near the Western Freeway roundabout opposite Toowong Cemetery about 3:50am on Sunday.

On Monday the officer in charge of the Brisbane Forensic Crash Unit, Senior Sergeant Simon Lamerton, said they were still piecing together details of Ms Humphrys' last movements.

"We think that Ashleigh has probably been either lying on the road or maybe on her hands and knees when she was stuck," Snr Sgt Lamerton said.

Police examine a skid where it is believed the sedan mounted the curb. ( ABC News )

"The injuries are consistent with that.

"It looks like she's certainly been intoxicated ... that's well reported at the moment."

Snr Sgt Lamerton said Ms Humphrys had been seen shortly before at a nearby service station.

"Some people tried to assist her with a taxi and she was not inclined to do that. They said she was intoxicated."

Snr Sgt Lamerton said police were running a number of inquiries, trying to find the driver of a dark sedan spotted in the area around the time Ms Humphrys was hit.

"It appears from the CCTV footage Ashleigh was walking towards the Western Freeway on the inbound side ... she walks just out of view of the CCTV then a taxi stops just past where she was last seen and was stationary for a number of minutes," Snr Sgt Lamerton said.

"Some other cars have filtered through at fairly low speed ... and then a dark coloured sedan has come through at a slightly higher speed.

"At this point that's the vehicle we're most interested in."

Snr Sgt Lamerton said they were hoping for some results in the new few days.

Senior Sergeant Simon Lamerton addresses the media. ( ABC News: John Taylor )

"If that person is watching ... we ask them to come forward and identify themselves to us and assist us in any way they can," he said.

Snr Sgt Lamerton said the taxi that was first on scene has been seized as part of the investigation.

"It was simply to rule it out as being involved and that's quite normal as a precaution in these types of matters," he said.

"We've got no evidence of the taxi being involved or the taxi driver."

Snr Sgt Lamerton said a second taxi may have been there - off to the side for a short time, away from the first taxi.

"If that driver could come forward to help us just to rule them out," he said.

"The footage is not of great quality and is from a distance - [it] may not even be a taxi."