Assistant Sacramento County Coroner Ed Smith said Saturday a preliminary investigation found evidence "consistent with a water intoxication death."
Jennifer Strange's mother found her daughter's body at her home Friday in the Sacramento suburb of Rancho Cordova, California, after Strange called her supervisor at her job to say she was heading home in terrible pain.
"She said to one of our supervisors that she was on her way home and her head was hurting her real bad," said Laura Rios, one of Strange's coworkers at Radiological Associates of Sacramento. "She was crying and that was the last that anyone had heard from her."
Earlier Friday, Strange took part in a contest at radio station KDND 107.9 in which participants competed to see how much water they could drink without going to the bathroom.
Initially, contestants were handed eight-ounce bottles of water to drink every 15 minutes.
"They were small little half-pint bottles, so we thought it was going to be easy," said fellow contestant James Year of Woodland, California. "They told us if you don't feel like you can do this, don't put your health at risk."
Ybarra said he quit after drinking five bottles. "My bladder couldn't handle it anymore," he added.
After he quit, he said, the remaining contestants, including Strange, were given even bigger bottles to drink.
"I was talking to her and she was a nice lady," Ybarra said. "She was telling me about her family and her three kids and how she was doing it for kids."
The winner of the "Hold Your Wee for a Wii" contest was promised a Nintendo Wii video game system.
John Geary, vice president and marketing manager for Entercom Sacramento, the station's owner, said station personnel were stunned when they heard of Strange's death.
"We are awaiting information that will help explain how this tragic event occurred," he said.