A Grande Prairie nurse has pleaded guilty to administering sedatives to her co-workers.

Sarah Christine Bowes, 27, was to face a preliminary hearing Monday. Instead she pleaded guilty to 12 charges, including administering the drug, using credit cards obtained through crime, and public mischief for trying to implicate someone else.

In early 2004, staff members at the Queen Elizabeth II Hospital in Grande Prairie began reporting flu-like symptoms, memory loss and spending more time than usual sleeping.

They said the illnesses continued for 17 months before suddenly stopping.

The hospital closed the floor and conducted air-quality and environmental tests, but lab results found nothing unusual.

Around the same time, staff reported stolen personal belongings and credit cards. They also told hospital authorities that they couldn't find some of the hospital's prescription drugs.

The case baffled police for two years until Bowes was charged in March.

At the time, police alleged Bowes gave a prescription sedative in the benzodiazepine family of drugs to at least seven co-workers.

Alberta Union of Provincial Employees president Dan MacLennan said the plea comes as a relief to members of his union working at the hospital.

"Things were going missing and people were getting sick," he said.

"This had been something that had been going on for a long time and I think today it's really good news for moving forward for all the staff."

Bowes had been released on bail into the custody of her father in Little Current, Ont., who vociferously defended his daughter's innocence at the time of her arrest.

She is expected to be sentenced after victim impact statements are read in court later this week.

With files from the Canadian Press