Autumn Marie Klein, prominent Pittsburgh doctor, dead from cyanide poisoning

(CBS) PITTSBURGH - Homicide investigators are now looking into the case of Autumn Marie Klein, a doctor at the University of Pittsburgh Medical Center who died of cyanide poisoning on April 20, CBS Pittsburgh reports.

According to the station, Klein's husband, Dr. Robert Ferrant, called 911 on April 20 to report his wife had a heart attack.

It was later determined that "extremely high levels of cyanide" were found in Klein's blood and ultimately caused her death.

District Attorney Stephen Zappala told CBS Pittsburgh that Klein's death is being looked at as a possible homicide or suicide.

Allegheny County Medical Examiner Dr. Karl Williams says more tests need to be performed and that it is a very complex investigation.

Klein, 41, was chief of the division of women's neurology and an assistant professor of neurology, obstetrics and gynecology at UPMC's Presbyterian and Magee-Womens hospitals.

Her husband works as a neurology professor at the University of Pittsburgh.

The medical examiner's office has reportedly issued subpoenas to the university to gain insight into the movement of chemicals, including cyanide, in and out of the lab. CBS Pittsburgh reports search warrants are specifically being used to obtain cyanide from the lab where Ferrante works.

Ferrante has hired a prominent attorney, as well as former U.S. Attorney General J. Alan Johnson, the station says. He has also reportedly retained the help of forensic pathologist Cyril H. Wecht.

Klein came to Pittsburgh in 2011 from Boston's Brigham and Women's Hospital. She has a 6-year-old daughter.