Medical examiners' spokeswoman Julie Bolcer said there was no timetable for the autopsy to be finished. She declined to discuss the pending tests, but toxicology and tissue tests are typically done in such cases, according to the Associated Press. Police, meanwhile, have been investigating it as a suspected drug overdose and arrested four people with possible connection to Hoffman's death Tuesday night.
Hoffman was found dead in his West Village apartment Sunday morning. He was 46.
A police source told PEOPLE that the actor, who battled drug addiction throughout his life, was found with a syringe in his arm. Hoffman last sought treatment in May, when he entered rehab for heroin after staying clean for 23 years.
The father of three was in the midst of filming the first installment of The Hunger Games: Mockingjay at the time of his death. Just weeks ago, two of his movies, A Most Wanted Man and God's Pocket, premiered at Sundance.
Hollywood, meanwhile, mourned Hoffman's passing with praise-laden tributes, and the marquees of New York's Broadway theatres will be dimmed for one minute on Feb. 5 at 7:45 p.m. in his honor.
"This is a horrible day for those who worked with Philip," said Tom Hanks, who worked with Hoffman in Charlie Wilson's War. "Our hearts are open for his family."
For anyone wishing to celebrate or honor the great Philip Hoffman's life and work, this is a nice way to do it: http://t.co/zklE0oTLwm— Edward Norton (@EdwardNorton) February 3, 2014