A university graduate found in her burning car was probably killed before the vehicle was set alight, police have said.
Catherine Wells-Burr's remains were discovered in her red Ford Focus, which was abandoned in a field by the side of a road near Ilminster, Somerset, on September 12.
Fire crews extinguished the flames and discovered the body of the 23-year-old Bath Spa University graduate inside the wreckage.
Her boyfriend Rafal Piotr Nowak, 31, has appeared before magistrates in Bristol charged with conspiracy to murder her.
His former partner, Anna Julia Lagwinowicz, 32, faced the same charge at the same court the previous day.
Speaking outside court, 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."
He added: "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."
Det Ch Insp Crisp said "new lines of inquiry" had emerged after police had spoken to motorists along the A358, one week on from when Miss Wells-Burr's blazing car was discovered.
Nowak is charged with conspiring together with Lagwinowicz and others to murder his girlfriend, with the offence said to have been committed between May 1 and September 13.
His lawyer, Jeffrey Bannister, did not make an application for bail.
He told the court: "As a tragic consequence of this incident, my client is not able to go back to the address he shared with this young lady.
"As a result, he cannot put forward an address and will not be applying for bail."
Nowak, of Willow Way, Chard, Somerset, was remanded into custody to appear alongside Lagwinowicz at Bristol Crown Court on October 9.
A 38-year-old man arrested in connection with the inquiry remains in police custody.