The last reported sighting of Mr Bell was at his home in the Christchurch suburb of Dallington on Thursday morning.
Mr Bell's family and partner have been spoken to by police.
"At this stage the inquiry remains a suspicious death investigation.
"We are trying to put together a picture of the deceased's movements in the days leading up to his death.
"A key component to this investigation is determining when the car was burned out. We now believe this was prior to Thursday evening.
"A member of the public who was in the area has come forward to police and indicated they had seen the burned-out shell of the car at around 4pm to 5pm on Thursday."
Police have discounted bullet holes found in the side of the car being related to the fire or the death.
"A group of recreational shooters has come forward and told police they were in the vicinity on Friday evening.
"They have indicated that the car was already burned-out at that time, and that they fired shots at the vehicle using a rifle."
Police also want to hear about any sightings of the Subaru station wagon before Thursday evening.
Police expected to complete the scene examination at the Loburn site and to remove the vehicle yesterday afternoon.
Anyone with information about Mr Bell or the 1989 silver Subaru station wagon is asked to contact Christchurch police on (03) 363-7400, or anonymously to Crimestoppers on 0800 555 111.