Fairfax County police continued their investigation yesterday into the death of a 25-year-old woman found dead in her cell Saturday night in the county jail.

Police said the woman, identified as Phyllis Y. Sanders, lived at 1238 Oats St. NE in the District and worked as a waitress.

County police said they have not yet determined the cause of death and are awaiting the results of tests to be performed at the state crime laboratory in Richmond.

Chief Deputy Sheriff M. Wayne Huggins said yesterday Sanders was found at 11:50 p.m. Saturday lying with her feet on her bed and her face on the floor of a cell in the woman's section of the jail. Huggins said the woman had water in her lungs when police tired to revive her.

Sanders, who was charged with speeding and failure to stop by state police after a chase on I-95, was admitted to the jail Saturday morning and had "no injuries that we could ascertain," according to Fairfax County Sheriff James D. Swinson.

Huggins said Sanders accepted two aspirin from a jail paramedic, but refused any other medical attention. Huggins said Sanders was "belligerent" in the jail and that she refused to eat dinner Saturday night.

Huggins said Sanders was "checked on every 30 minutes" while in jail.

The death was the first in the new conty jail since it opened last fall, according to Swinson. He said his department is conducting an investigation.