An autopsy Wednesday morning on actor Heath Ledger was inconclusive, and a cause-of-death determination will take 10 to 14 days, a medical examiner's spokeswoman said.
Meanwhile, tests on a $20 bill found at the Lower Manhattan apartment where Ledger died yielded no drug residue, a New York police spokeswoman told CNN. The bill was collected for testing because of the way it was folded, New York Police Commissioner Ray Kelly said earlier.
The Academy Award-nominated actor was found dead Tuesday of a possible drug overdose, the New York Police Department said. He was 28.
New details are emerging about the moments before and after his death.
The masseuse who discovered Ledger's body called his friend -- actress Mary-Kate Olsen -- twice before calling 911, a police source with knowledge of the investigation said.
A housekeeper, identified by the source as Teresa Solomon, arrived at the apartment about 12:30 p.m. Tuesday, the police source said.
She went into Ledger's bedroom to change a light bulb in an adjoining bathroom about 1 p.m., saw him on the bed face down with a sheet pulled up around his shoulders and heard him snoring, the source said.
Masseuse Diana Wolozin arrived at the apartment about 2:45 p.m. to give Ledger a massage, according to the police source. About 15 minutes later, when he had not come out of the bedroom and the door remained closed, she went in, saw him lying in bed, and set up a massage table nearby.
She shook Ledger, but he did not respond, so she used his cell phone to call Olsen in California, knowing Olsen was a friend of Ledger's, the source said.
Wolozin told Olsen that Ledger was unconscious, according to the NYPD source.
Olsen told her she would call private security people in New York. After getting off the phone, Wolozin tried to wake Ledger again, then called Olsen back to tell her she believed the situation was an emergency and was calling 911.
In the 911 call, at 3:26 p.m., Wolozin told authorities Ledger was not breathing. While on the phone with dispatchers, Wolozin tried to perform CPR on Ledger, but he was unresponsive.
Emergency personnel arrived seven minutes later, according to the police source, at about the same time as a private security person summoned by Olsen.
The medical technicians performed CPR on Ledger and used a cardiac defibrillator, but their efforts were in vain and he was pronounced dead at 3:36 p.m. By then, two other private security people summoned by Olsen had arrived, as well as police.
Ledger's former girlfriend, actress Michelle Williams, who was shooting a movie in Sweden, was informed of his death late Tuesday night, a movie production company spokesman said.
Williams left early Wednesday morning with 2-year-old daughter Matilda Rose, the spokesman said. Ledger was the child's father.
Some prescription medications were found in the room where Ledger -- Oscar-nominated for his role in "Brokeback Mountain" -- died, said police spokesman Paul Browne.
He said the pills were not "scattered around," as had been reported.
No note was found, and there was no indication of foul play, Browne said.
In light of Ledger's death, President Bush on Wednesday postponed an event surrounding the launch of a public-service ad campaign warning against the dangers of prescription drug abuse.
"We thought it would be better to postpone the event rather than run the risk of anyone thinking that we were being opportunistic in highlighting the issue," White House spokeswoman Dana Perino said.
Ledger's family on Wednesday called his death "very tragic, untimely and accidental."
Condolences began pouring in from Ledger's friends and co-stars.
"I had such great hope for him," said Mel Gibson, who played Ledger's father in "The Patriot," in a statement.
"He was just taking off, and to lose his life at such a young age is a tragic loss. My thoughts and prayers are with him and his family."
At the time of his death, Ledger had just finished playing the villain The Joker in "The Dark Knight," the latest installment in the Batman series. The film is to open in July.
The role disturbed him, according to The Associated Press. He called The Joker a "psychopathic, mass-murdering, schizophrenic clown with zero empathy."
"Last week, I probably slept an average of two hours a night," Ledger told The New York Times. "I couldn't stop thinking. My body was exhausted, and my mind was still going."
He said prescription sleeping pills didn't help, according to AP.
Ledger was born in Perth and named Heathcliff Andrew after the main characters of Emily Bronte's "Wuthering Heights." He began acting at a local theater as a child.
Ledger's first American film was the teen comedy "10 Things I Hate About You" in 1999, and he immediately attracted attention from Hollywood. He passed up several scripts before taking a role in the Revolutionary War drama "The Patriot" in 2000 and "A Knight's Tale" in 2001. He also played a supporting role in "Monster's Ball," among other films.
But Ledger was perhaps best known for his 2005 portrayal of Ennis Del Mar in "Brokeback Mountain," about two cowboys who had a secret romantic relationship. The role earned him an Oscar nomination.
Asked how he felt about filming love scenes with another man, Ledger said he and his co-star Jake Gyllenhaal simply focused on their roles.
"We can't say that we weren't nervous about it," Ledger told Oprah Winfrey in 2006. "But once the first take was over, it's like, 'OK. So what? It's kissing another human being. How are we going to finish this scene? Let's get on with it and let's get out of here.' "
In a written statement, the Gay and Lesbian Alliance Against Defamation said it mourns Ledger's death, adding that his portrayal of Del Mar "changed hearts and minds in immeasurable ways."
CNN's Deb Feyerick, Susan Chun, Miguel Susana and Eden Pontz contributed to this report.