Police sources say Hoffman was found unconscious at around 11:15 this morning on the bathroom floor of his New York apartment at 35 Bethune St. in the West Village neighborhood of Manhattan by friend and screenwriter David Katz, who called 911. He was pronounced dead at the scene.
The cause of death has not yet been determined, but a law enforcement official tells ABC News heroin was found at the scene and a hypodermic needle was sticking out of Hoffman's arm. The New York Police Department is continuing to investigate.
Results from the NYC Office of Chief Medical Examiner on the exact cause of death are expected on Monday.
Hoffman's family released the following statement on the actor's untimely death this afternoon:
"We are devastated by the loss of our beloved Phil and appreciate the outpouring of love and support we have received from everyone. This is a tragic and sudden loss and we ask that you respect our privacy during this time of grieving. Please keep Phil in your thoughts and prayers."