A 14-year-old Santa Rosa girl died early Sunday at a sleepover party after she and three of her friends drank an unknown substance mixed with soda and became violently ill, Sonoma County sheriff's officials said.

The girl, whose identity was withheld, was found dead on her bedroom floor at about 9 a.m., Lt. Steve Brown said. Sheriff's officials then asked the other parents to take their daughters to the hospital to be evaluated, he said.

Detectives were investigating the death as suspicious and waiting for toxicology reports to determine what the girls mixed with the soft drink, Brown said.

"We don't know if it was alcohol-related," said Brown. "They were all violently throwing up."

The teen's mother and stepfather hosted a sleepover for their daughter and her three friends at their Foothill Ranch Road home in a hillside neighborhood east of Mark West Springs Road, Brown said.

The teen's mother woke up sometime around 2 or 3 a.m. and found that two of the girls were throwing up, Brown said.

The girls said they were sick from food, and the mother cleaned them up and put them back to bed, he said. About an hour later, the mother woke up again and the other two girls, including her daughter, were up and vomiting, according to Brown.

"She assumed it was food poisoning," Brown said. "She cleaned them up and they went back to sleep."

In the morning, two of the girls were picked up by their parents. The third friend was in the shower when one of the deceased teen's parents tried to wake her, Brown said.

She was unresponsive and they called 911. Paramedics determined that she was dead.

The girls told authorities that their friend had passed around a soda that they all drank and that it tasted strange, Brown said. They told detectives that they didn't know what was in the drink.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com.