Halifax police were called to the Central Nova Scotia Correctional Facility in Burnside after an incident at the jail Monday afternoon around 4 p.m., according to the province's Department of Justice.
"Three offenders suffered relatively minor injuries," said Chad Lucas, a department spokesman.
"One was treated on site, one refused health care and one was transported to hospital."
He would not disclose how the incident began or the extent of the injuries.
Police said they expect to lay charges.
In addition to a police investigation, staff at the jail will also be conducting an internal investigation into the incident.
According to Lucas, the facility is back under control.