Leanne Thomson, 17, was found by police in a red Rover 214, owned by her boyfriend, in a car park in Drummuir, Moray, at about 0700 BST on Sunday.
The village is about five miles from her home in Keith.
A spokesman for Grampian Police said the death was being treated as "suspicious" and described it as a "major incident" involving more than 30 officers.
The police spokesman refused to comment on the nature of the teenager's injuries, saying officers were awaiting the results of a post-mortem examination.
The girl's boyfriend, 20-year-old James Williamson, was taken to Dr Gray's Hospital in Elgin on Sunday morning after taking ill. A condition report was unavailable.
A police spokesman said: "We will be interviewing him along with other people - he's one of a number of people that we will be speaking to.
"We are not saying anything about the injuries or what she may have died of.
House inquiries
"We are waiting for the results of the post-mortem, which could be finished later today or tomorrow."
Detective Inspector Gordon Symonds, who is the senior investigating officer, said: "Our inquiries are with more than 30 officers and we are following several lines of inquiry.
"The house-to-house inquiries are ongoing in the Drummuir and Keith areas.
"We are speaking to a lot of people in connection with this inquiry, including members of her family, and we are trying to build up a picture of Leanne and her movements."
DI Symonds said the police were particularly keen for anyone who might have seen Leanne in the hours leading up to her discovery to get in touch.
He added the car had been removed to force headquarters in Aberdeen for a forensic examination.