Hoffman, 46, was found in the bathroom of the fourth-floor apartment, the sources told CNN.
Police found what they believe to be heroin inside the apartment, a source told CNN.
Hoffman’s body was discovered by a playwright who had been working with him.
A needle was found in one of the actor’s arms, the sources told CNN.
Hoffman won an Academy Award for best actor for the 2005 biopic “Capote.”
He was a beefy 5-foot-10-inch man, but was convincing as the slight 5-foot-3-inch Truman Capote. He had a booming voice like a deity’s but often played shlubby, conflicted characters.
He could be heartfelt and giving, as with his male nurse in “Magnolia” or rock critic in “Almost Famous,” or creepily Machiavellian, like the gamemaster in the latest “Hunger Games” movie or a “Mission: Impossible” movie villain.
He also appeared in “Charlie Wilson’s War,” “Doubt,” and “The Master,” for which he was nominated as best supporting actor.
According to a biography of the actor posted on the Turner Classic Movies website, last year Hoffman revealed he was seeking treatment for drug abuse, and “seemed to be confident that he was getting a handle on the situation.”
Hoffman’s father was a salesman and his mother was a family court judge, the biography says.
He landed his first professional stage role before graduating from high school and went on to study acting at New York University.
In Hollywood, his big break came with a small role as Chris O’Donnell’s classmate in the 1992 film “Scent of a Woman.”
For years, Hoffman was the kind of anonymous character actor who earned critical raves but was often unnoticed by the general public. He used his abilities to take chances with such directors as a then-unknown Paul Thomas Anderson, with whom he worked in “Hard Eight” (and several ensuing films, as both became better known) and Todd Solondz (“Happiness”).
“I think about that a lot,” he told Esquire in 2012 of his anonymity. “I feel it cracking lately, the older I’m getting. I think I’m less anonymous than I was.”
Even after winning the Academy Award, he took challenging roles. He was an L. Ron Hubbard-style leader in “The Master” and an intense theater director in “Synecdoche, New York.” Neither lit up the box office, but Hoffman’s performances earned wide praise for their immersiveness.
Hoffman appeared last month at the Sundance Film Festival, where a movie he starred in, “God’s Pocket,” premiered.
After his Oscar win at the Academy Awards in 2006, Hoffman thanked his mother for taking him to his first play.
“She brought up four kids alone and she deserves a congratulations for that. Ah, we’re at the party, Ma, you know? And she took me to my first play and she stayed up with me and watched the NCAA Final Four, and my passions, her passions became my passions. And, you know, be proud, Mom, because I’m proud of you and we’re here tonight and it’s so good,” he said in his acceptance speech.
Hoffman stayed active on stage even as his star rose in Hollywood. He starred in a Broadway production of “Death of a Salesman” in 2012 and was co-artistic director of the Labyrinth Theater Company in New York.
He is survived by three children and his longtime partner, Mimi O’Donnell.
CNN’s Susan Candiotti and Shimon Prokupecz contributed to this report.
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By Steve Almasy
The-CNN-Wire™ & © 2014 Cable News Network, Inc., a Time Warner Company. All rights reserved.