Three correctional workers at a Kitchener, Ont. prison for women were charged Thursday in connection with an inmate's death.

Emergency crews were called to the Grand Valley Institution for Women in Kitchener, Ont. last Friday to help an inmate identified as Ashley Smith, 19, of New Brunswick by Waterloo Regional Police.

An autopsy concluded she died of asphyxiation, which investigators said was self-initiated. Waterloo regional police said there were no other injuries or trauma to Smith's body.

The three workers are charged under a section of the Criminal Code that relates to "omitting to do anything that it is his (or her) duty to do, shows wanton or reckless disregard for the lives or safety of other persons."

Earlier Thursday, dozens of unionized workers conducted information pickets outside the prison.

Several other employees, including one supervisor, have been suspended without pay. The Union of Canadian Correctional Officers said that's contrary to their collective agreement.

According to police, Smith was found in her cell and transported to hospital where she was pronounced dead. She had been serving a six-year, one-month sentence for offences committed as a young offender.

"A post-mortem examination has been completed and the cause of death determined to be asphyxiation which investigators have been determined to be self-initiated. There were no other injuries or trauma to the deceased," Larkin said in a press release."

Initially, no foul play was suspected, but Larkin said some "pieces of evidence" led to a criminal investigation.

Smith had begun serving her sentence on Oct. 17, 2003, but it is common for inmates serving sentences of two years or more to be transferred to adult federal facilities once they hit a certain age.

The Correctional Service of Canada plans to conduct its own investigation into how Smith died. A coroner's inquest will also be held.

"The corrections investigation will review the circumstances surrounding the incident, including any issues of compliance with the law, policies and procedures," Public Safety Minister Stockwell Day said in a news release.

"This incident is extremely disturbing and of serious concern to me. I expect that it will be addressed in an expedient, efficient and sensitive manner, after which appropriate action will be taken."

Karen Eves, 52, Valentino Burnett, 47, and Blaine Phibbs, 31, are all charged under Section 220 (b) of the Criminal Code, Causing Death by Criminal Negligence. The charge relates to "omitting to do anything that it is his duty to do, shows wanton or reckless disregard for the lives or safety of other persons."