A mystery substance has shut down Coulee Medical Center after three employees in the lab area became ill for unknown reasons Tuesday afternoon.

CMC was evacuated and employees sent home, and a hazmat team has been requested to investigate.

No one knows what made the lab workers ill, other than an odor, but their conditions were apparently not serious. It started with headaches, then chest pains, shortness of breath and vomiting. They've been checked out and released.

No patients were affected, said Ramona Hicks, chief executive officer. After they were evacuated, all staff were sent home. She wasn't sure how many had been in the building at the time.

Eight long-term care residents and five acute care patients were taken to other hospitals, including those in Ephrata, Omak, Davenport, and Moses Lake.

Hicks said they were grateful for quick co-operation.

Ambulances from neighboring towns were taking turns loading up patients for transport to those other facilities Tuesday afternoon. In addition to three local ambulances from Grand Coulee, several from Hartline, Coulee City and Omak came and left with patients between 4:30 and 5:30 p.m.

While the main hospital building is closed, Hicks said, hospital staff are converting the Medical Arts building - where doctors at the drop-in clinic normally see patients - to an urgent-care clinic for immediate and urgent patient needs only.

Hicks said hospital officials would meet at 8 a.m. Wednesday with incident command on the status of the investigation. She said hazardous materials investigators would be coming from either Spokane or Fairchild Airforce Base.

Unknown at this writing Tuesday night is a re-opening date for the hospital. Sharon Gilmore, in charge of risk management at CMC, said that if a flush of the central air systems is necessary, that would likely take two days.

Gilmore said some patients with appointments would be called to reschedule.

Grand Coulee fire crews had been on their way out of town to help fight a wildfire near Soap Lake when they heard the call to respond to CMC for a possible gas leak and had to turn around.