An officer at the hospital became ill after investigating the bag's contents. He complained of a sore throat and nausea.
Hospital personnel called the Fire Dept., who responded, evaluated the scene, and called in the Hazardous Materials team.
One portion of the Emergency Dept. was isolated while a sample from the bag was retrieved. Authorities expect to identify the bag's contents Friday afternoon.
The hospital continues to operate normally. No other injuries or effects have been reported.
Hours later, a fire captain said the mysterious substance was powdered alfredo sauce mix.
The woman and the officer are both in good condition.