Whitney Houston was still alive when paramedics arrived at a Beverly Hills hotel room and found the singer unconscious in the bathtub, according to reports.
But emergency crews were unable to revive the stricken singer on Saturday afternoon, and she was later pronounced dead.
There have been reports that the troubled singer was drinking and using prescription drugs before her death, but it's not clear what killed the 48-year-old star.
Meanwhile, it's believed that Houston's funeral will take place in her home state of New Jersey later this week.
Houston's body was flown back to New Jersey from California on Monday evening.
There are also reports that a wake for the late singer may be held at the Prudential Center in Newark, which is a large arena that holds about 18,000 spectators.
Earlier on Monday, Beverly Hills police revealed that Houston was under water and apparently unconscious when she was found in a hotel bathtub.
Officials say that there was water in her lungs, but not enough to be fatal.
At a news conference, Lt. Mark Rosen said Houston, was found Saturday by members of her personal staff at roughly 3:30 p.m. local time.
Rosen said she was pulled from the tub and hotel security was promptly notified about the incident.
No other details are being released until the investigation is complete, he said.
Toxicology tests are being carried out by the coroner's office, but it could be weeks before the true cause of death is known.
The Los Angeles coroner's office said Sunday the post-mortem exam revealed no signs of foul play.
The coroner's office said Sunday there were no visible signs of trauma on Houston's body but they added that they were not ruling out any causes of death until they have the results of toxicology tests.
Those tests could take six to eight weeks to complete, but the coroner's office was said to be releasing the body to Houston's family on Monday.
Gossip website TMZ cited "law enforcement sources" in its report that police had retrieved about half a dozen pill bottles from Houston's room, including bottles of Xanax, but there was no evidence of illicit drug use.
Assistant Chief Coroner Ed Winter declined to say anything about any evidence police recovered from the hotel room.
"I'm not going to comment on any of the meds or prescriptions that were obtained," he told reporters Sunday.
"I'd just comment that she was found in the bathtub. ... I believe somebody removed her from the bathtub and the paramedics did CPR (cardiopulmonary resuscitation) on her."
Winter said a "security hold" had been placed on the investigation, as has been done in previous high-profile deaths, to keep further details from being leaked.
According to TMZ, the post-mortem exam revealed water in Houston's lungs, suggesting she was alive when she slipped under the water and breathed the water in.
But it's unclear whether the singer died by drowning or whether any drugs or alcohol in her system caused an overdose death.
Houston reportedly had been taking Xanax for some time to help calm her nerves -- especially before big shows such as the pre-Grammy party she was scheduled to perform at on Saturday night.
Xanax is the brand name for alprazolam, a medication used to treat anxiety and panic disorders. It is part of a class of medications called benzodiazepines which act on the brain and nerves to produce a calming effect.
According to the medication monograph, Xanax should not be mixed with alcohol because it can cause life-threatening depression of the central nervous system. That could lead to stupor, coma or death.
Xanax is also addictive and users must wean off it gradually to avoid dangerous withdrawal symptoms, such as seizures.
The risk of addiction is increased at higher doses and with longer term use. The risk is further increased in patients with a history of alcohol or drug abuse.
"Addiction-prone individuals should be under careful surveillance when receiving alprazolam," the monograph reads.
Meanwhile, Houston's 18-year-old daughter, Bobbi Kristina, has been released from hospital after being treated for "stress" and "anxiety" following her mother's death.
On Monday evening, a White House statement said that U.S. President Barack Obama's thoughts and prayers were with Houston's family and friends.
