Police investigating the death of Catherine Wells-Burr "strongly suspect" she was already dead before last Wednesday morning's car fire.
In a new development, the man leading the investigation into her death said he believed that Catherine was "murdered in the early hours of last Wednesday morning" and then transported to the scene of the fire.
Her Ford Focus was discovered on fire in a lane at Ashill near Ilminster a week ago. The 23-year-old, from Chard, was found inside.
Detective Chief Inspector Simon Crisp said: "We are in possession of information that leads us to strongly suspect that Catherine didn't die in the fire.
"We believe she was murdered in the early hours of last Wednesday morning and she was transported to the scene of the fire, which was lit at about 6am.
"So we are really keen to speak to anybody who may have seen Catherine's car, which was also transported at the same time.
"We think potentially that car was in the company of another vehicle around the Chard area in the very early hours, travelling around Chard along the A358 to Ashill.
"If anybody sighted that red Ford Focus by itself or with another vehicle, I am really keen to speak to them."
This afternoon, police also said that a 38-year-old man arrested in connection with the murder of Miss Wells-Burr has been released on bail pending further enquiries.
Anyone with information should call police on 101 or Crimestoppers on 0800 555 111.