Police told the news agency that more toxicology tests are necessary, and results will take two to four weeks.
The 27-year-old singer was found dead in her London home Saturday. Before the autopsy, police stated that the death was being treated as "unexplained and there have been no arrests in connection with the incident."
Meantime, a family spokesman said the funeral will take place Tuesday for family and close friends. He said the time and place won't be disclosed.
The singer's parents and brother stopped by her house Monday to see the heaps of bouquets, candles and handwritten notes left nearby. The AP reported that her father, Mitch Winehouse, thanked mourners for their tributes; her mother, Janis, was in tears. Many of the sentiments read the same: "What a waste."