According to multiple US reports, law-enforcement officials carried out a raid on Tuesday night. Three men — two in their 50s and one in his 20s — and a woman in her 20s were detained and questioned. They are suspected of supplying the heroin that killed the 46-year-old star.
The arrest took place after police received a tip that the drugs found in Philip's apartment came from a Chinatown building.
The body of the Oscar-winning actor was found shortly after 11.30am on Sunday. He was the victim of an apparent drug overdose.
A private funeral service is scheduled to take place in Sunday in New York City, and plans are underway for a memorial service, also in New York, later this month.
On Wednesday night, the Broadway theatre district will dim its marquee lights for one minute at 7.45pm in Philip's memory.
Since the news of his passing broke, some of Hollywood's biggest names have visited the West Village home of Philip's former partner Mimi O'Donnell to pay their respects.
Joaquin Phoenix, Ethan Hawke, Cate Blanchett, Justin Theroux, director Paul Thomas Anderson and photographer Annie Leibovitz have been among those offering their condolences to the devastated mother-of-three, who spent 14 years with the actor.
Many of the visitors, including Cate, brought gifts for the couple's three children, Cooper, ten, Tallulah, seven, and five-year-old Willa.
Philip's grieving mother, Marilyn O'Connor, was also seen arriving at the Manhattan apartment on Tuesday to spend time with her grandchildren. Mother and son were very close; Philip dedicated the Academy Award he won for Capote to Marilyn.