They said they were awaiting test results before determining the cause of death.
In determining the cause of death in most routine autopsies, a pathologist offers his or her "best medical opinion".
But determining what causes a behavior can be even more complicated than determining the cause of a disease.
Canada stands ready to provide whatever support it can to assist authorities in determining the cause of the crash".
She made frequent televised appearances in October to describe progress in determining the cause of the crash of American Airlines flight 587, in Queens.
They confirmed they impounded the car because "it may contain medications or evidence that may assist the coroner in determining the cause of death".
A medical examiner had previously ruled her death accidental, determining the cause to be "excited delirium" with McKenna's schizophrenia listed as a contributing factor.
David Glassman, chairman of the anthropology department at Southwest Texas State University, said determining the cause of death could take a month.
Park spokeswoman Sharon Parker said: "We are committed to determining the cause of this tragic accident and will utilise every resource throughout this process.
"We must put all our effort into determining the cause of the accident and to ensuring safety," Prime Minister Junichiro Koizumi said Tuesday.
But Canadian officials say they are still far from determining the cause of the crash, which killed 129 people off Nova Scotia.
