Oscar-winning actor Philip Seymour Hoffman was found dead in his New York City apartment Sunday, Feb. 2 of an apparent drug overdose, law enforcement sources said.

Hoffman, 46, was allegedly found on the bathroom floor and pronounced dead at the scene.

A needle was in the actor's left arm, and some empty glassine-type bags were found in the apartment, law enforcement sources said. He was wearing shorts and a T-shirt with his eyeglasses still resting on his head.

The empty bags were stamped with apparent street names for heroine: "Ace of Hearts" and "Ace of Spades.”

Investigators later discovered close to 50 envelopes of what they believed was heroin in the apartment. They also found used syringes and prescription drugs.

Hoffman was expected to get his children on Sunday, but didn't show up. Playwright David Katz and another person went to the apartment and found him dead, police said.

Four people believed to be connected to the drugs found in Philip Seymour Hoffman's apartment were arrested late Tuesday night, law enforcement officials told CNN.

Apartments at 302 Mott Street in Manhattan, where the four were arrested, are now part of the investigation into Hoffman's death, according to a police source.

The source identified the suspects being investigated in connection with drugs sold to Hoffman as Juliana Luchkiw, 22, charged with criminal use of drug paraphernalia, criminal possession of a controlled substance and unlawful possession of marijuana; Max Rosenblum, 22, charged with criminal use of drug paraphernalia, criminal possession of a controlled substance and unlawful possession of marijuana; Robert Vineberg, 57, charged with criminal possession of a controlled substance and criminal use of drug paraphernalia; and Thomas Cushman, 48, charged with criminal possession of a controlled substance.

Vineberg was found to have the actor's phone number stored in his cell phone, a law enforcement official told CNN.  Police discovered the largest amount of what is believed to be heroin in his apartment, the source said.

In a 2011 interview with "60 Minutes," Hoffman discussed his past struggles with drug and alcohol addiction.

"Anything I could get my hands on, I liked it all," he said.

He had sobered up for a time, but last year, Hoffman said he'd fallen off the wagon, started taking prescription pills and slipped into snorting heroin again, according to TMZ.

Magazine writer John Arundel said he saw Hoffman at the Sundance Film Festival in Utah two weeks before his death.

"I said, 'What do you do?' And at that point, he took off his hat and he said, 'I'm a heroin addict,'" Arundel said. "Didn't look like he was (joking). Seemed like he was having one of those 'coming to God' moments -- where it just struck him as, 'this is the revelatory moment.'"

Hoffman appeared on Broadway three times. He won an Academy Award for best actor for the 2005 biopic Capote and drew critical acclaim for his roles in a wide variety of films.

He is survived by his three children Tallulah Hoffman, Cooper Alexander Hoffman, Willa Hoffman and his partner for 15 years, costume designer Mimi O'Donnell.