On a tape of the Jan. 12 show, disc jockeys on KDND-FM's "Morning Rave" joke about the possible dangers of consuming too much water, at one point alluding to a college student who died during such a stunt in 2005.
During the contest, a listener - self-identified as a nurse - called the live radio broadcast and warned that the game was dangerous, CBS News station KOVR-TV reported.
"I want to say that those people drinking all that water can get sick and die from water intoxication," said the caller.
"Yeah, we're aware of that," one of them said.
Another DJ laughed: "Yeah, they signed releases, so we're not responsible. We're OK."
"And if they get to the point where they have to throw up, then they're going to throw up, and they're out of the contest before they die, so that's good, right?" another one said.
The Sacramento County Sheriff's Department decided to pursue the investigation Wednesday after listening to the tape, obtained by The Sacramento Bee newspaper, sheriff's spokesman Sgt. Tim Curran said.
Jennifer Lea Strange, a 28-year-old mother of three, was one of about 18 contestants who tried to win a Nintendo Wii gaming console by determining how much water they could drink without going to the bathroom. The show's DJs called the contest "Hold your Wee for a Wii."
"Hey, Carter, is anybody dying in there?" a DJ asked during the show. "We got a guy who's just about to die," the other responded, and all the DJs laughed.
"I like that we laugh about that," another said.
"Make sure he signs the release. ... Get the insurance on that, please."
Strange participated in the contest during the morning in the studio and was found dead that afternoon. The county coroner said preliminary autopsy findings indicate she died of water intoxication.
Other contestants said Strange may have ingested as much as two gallons of water. Several hours into the contest, Strange was interviewed on the air and complained that her head hurt.
"They keep telling me that it's the water. That it will tell my head to hurt and then it will make me puke," she said.
Strange won the second-place prize, tickets to a Justin Timberlake concert. She commented on the tape that she looked pregnant, and a female DJ agreed.
"Oh, my gosh, look at that belly. That's full of water. ... Come on over, Jennifer, you OK?" the DJ asked. "You going to pass out right now? Too much water?"
The winner of the contest, Lucy Davidson, said she collapsed just 15 minutes after leaving the station with her prize. "I didn't know what was wrong with me. I just knew I had never felt so sick in my life," Davidson told KOVR.
Davidson said Strange's stomach protruded over her waist as the contest ended.
"As soon as we went to the bathroom we both came out of the stalls. I looked over at her and she probably looked as pale as I did," Davidson said.
On Tuesday, KDND's parent company, Entercom/Sacramento, , including three morning disc jockeys. The company also took the morning show off the air.
Station spokesman Charles Sipkins said Wednesday that the company had not yet heard from the sheriff's department but that it would cooperate with the investigation.
Attorneys for the Strange family said Wednesday they plan to file a wrongful death lawsuit against the radio station.