A 44-year-old woman died and two other people were knocked out cold after they all took the club drug known as GHB, authorities said.
Gamma-hydroxybutyrate is known as a date-rape drug because of its depressive properties. It has also been used by body builders because it can help promote muscle growth.
The substance's euphoric effects are revered by some users in the club and rave scenes, but experts say its use can result in sleep, coma and death.
Once legal as a prescription drug, it was outlawed completely following the Date-Rape Drug Prohibition Act of 1999.
One of four victims called 911 at 4:46 a.m. Sunday, a fire official said. Paramedics and police responded to a residence at 23rd Avenue and Speedway near the Venice boardwalk, authorities said.
The 44-year-old, along with a 28-year-old man and a 25-year-old woman, were hospitalized, officials said. The 44-year-old, who was in full cardiac arrest, died, they said.
The other two were in bad shape but ultimately were stabilized, a Los Angeles Police Department official said.
"From the beginning we didn't know if they were going to make it or not," Lt. John Radtke told reporters at the scene. "But right now they are stable."
The other reported GHB taker didn't require hospitalization.
The four had been partying in a hot tub at an apartment belonging to the women, according to ABC Los Angeles.
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Homicide detectives were at the scene yesterday, but so far authorities don't suspect foul play.
"Right now it looks like it's accidental death because it does appear everyone used this drug voluntarily," Radtke said.
Toxicology tests, which take as long as six weeks, will help determine if GHB is officially to blame.