Police investigating the apparent drug overdose death of actor Philip Seymour Hoffman executed search warrants at a Chinatown apartment building Tuesday evening, seizing heroin and marijuana and arresting three men and one woman.

An NYPD spokesman said Wednesday police have not uncovered any direct links between the drugs recovered during the raid at 302 Mott St. and the death of Hoffman, who was found Sunday morning in the bathroom of his Greenwich Village apartment -- a needle in his arm.

An autopsy, meanwhile, was concluded but the cause of death is pending the results of toxicological tests in a few days, the office of the city's chief medical examiner said Wednesday.

The Academy Award-winning star had stockpiled more than 50 glassine envelopes of heroin, bearing the labels "Ace of Spades" and "Ace of Hearts," as well as prescription muscle relaxants and blood pressure pills, police said.

The heroin recovered during the arrests on Mott Street Tuesday did not bear similar labels, police said, but the investigation into any links between the heroin is continuing.

The search warrants were executed by NYPD 9th Precinct officers sometime after 6 p.m., police said. A total of three apartments were searched.

Arrested were: Thomas Cushman, 48, of 396 Vanderbilt Ave., Brooklyn, charged with misdemeanor criminal possession of a controlled substance; Max Rosenblum, 22, and Julianna Luchkiw, 22, both of 302 Mott St., who each were charged with misdemeanor criminal use of drug paraphernalia, misdemeanor criminal possession of a controlled substance, and unlawful possession of marijuana; and, Robert Vineberg, 57, of 302 Mott St., who was charged with felony criminal possession of a controlled substance, criminal use of drug paraphernalia and misdemeanor criminal possession of a controlled substance.

Arraignment details were not immediately available.

The NYPD and Drug Enforcement Administration officials said Monday that the two types of heroin recovered from Hoffman's apartment have not been seen often in the metropolitan area.

In one 2009 case DEA agents came across a single-sample "Ace of Spades" in Suffolk County. The NYPD found a sample of "Ace of Hearts" during a Queens investigation in 2012, one official said.

Hoffman's death comes at a time when the city has seen a spike in fatal accidental heroin overdoses. A Department of Health report released in September showed such deaths increased by 76 percent from 2010 to 2012. Those trends translated to a 71-percent increase in the rate of heroin deaths per 100,000 residents, city special narcotics prosecutor Bridget Brennan said.

Most heroin flooding New York City today originates in South America, primarily Colombia, where drug cartels send it into the United States through Mexico or various ports, Brennan said in an interview. The purity can range as high as 80 percent to as low as 20 percent, she noted.

Meanwhile, officials were trying to determine if the heroin recovered from Hoffman's apartment was adulterated in a way that made him overdose.

Fentanyl, another opioid derivative, is used by heroin dealers to give a double whammy to their product. The NYPD could not immediately say if the heroin recovered from Hoffman's apartment -- or, if the heroin recovered during the raid on Mott Street on Tuesday -- contained fentanyl.

Citing a police official, The Associated Press reported that the heroin tested negative for fentanyl.