Jennifer Strange, 28, was found dead in her home in Rancho Cordova, California, on Friday after drinking as much water as she could without going to the toilet

A preliminary investigation by the local coroner determined that her death was "consistent with a water intoxication death". It is not yet known how much water she drank.

Ms Strange, a mother-of-three, had taken part in radio station KDND 107.9's "hold your wee for a Wii" contest, in a bid to win a Nintendo Wii video games system.

Laura Rios, one of Ms Strange's colleagues at Radiological Associates of Sacramento, said Ms Strange had complained of a severe headache after participating in the contest.

Ms Rios said: "She said to one of our supervisors that she was on her way home and her head was hurting her real bad. She was crying and that was the last that anyone had heard from her."

John Geary, the vice-president and marketing manager for Entercom Sacramento, the station's owner, said staff were stunned when they heard of Ms Strange's death.

"We are awaiting information that will help explain how this tragic event occurred," he said.

Contestants were initially handed eight-ounce (225 milliliters) 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 Ybarra of Woodland, California. "They told us if you don't feel like you can do this, don't put your health at risk."

Mr Ybarra said he quit after drinking five bottles. "My bladder couldn't handle it anymore," he added.

But he said the remaining contestants, including Ms Strange, were given even bigger bottles to drink.

He said: "I was talking to her and she was a nice lady. She was telling me about her family and her three kids and how she was doing it for her kids."

Water intoxication, also known as hyponatremia, is extremely rare and only usually affects endurance athletes, such as long distance runners.

The condition is caused by a loss of sodium in the blood due to sweating and dilution by drinking large volumes of water. Typical symptoms include nausea, vomiting and headache. In the most serious cases the brain swells causing confusion, seizures, coma and even death.