New Twist in Brittany Murphy Death

Brittany Murphy's death investigation has taken a mysterious turn -- the L.A. County Coroner's Office is now trying to fill in some critical gaps in her medical history ... sources tell TMZ.

We've learned Brittany was suffering from severe anemia and other conditions and was under a doctor's care. The Coroner's Office received medical files from her doctor ... but they show her last visit was months before her death.

We're told the pathologist assigned to the case has been told by Murphy's friends and family that other doctors treated Murphy during her final months. The Coroner's Office is looking for the other doctors to determine her medical condition leading up to her death.

The pathologist also wants to know what medications may have been prescribed by the other doctors.

The toxicology report is not completed. Once the report reveals the drugs in Brittany Murphy's system at the time of her death, the Coroner's staff will then determine if the medications were prescribed to Brittany or, possibly, someone else.

As we first reported, investigators found numerous medications in Murphy's home after her death -- medications prescribed to Murphy, Simon Monjack, Brittany's mother Sharon Murphy and "unidentified third party names."

We're told the Coroner will not release the cause of death for weeks.