Overcrowding may have played a role in the death of an inmate at the Windsor Jail.
Kendra Blackbird was found unresponsive in her cell on Saturday and later died in hospital on Monday.
Dan Sidsworth is the provincial chair of the Ontario Public Service Employees Union's corrections division.
He claims Blackbird died of a drug overdose.
Sidsworth said that Blackbird was sharing a cell with an inmate who was only serving time on the weekends.
Those inmates are stripped searched, but correctional officers do not perform an internal search of their bodies, he said.
Sidsworth said the policy is to keep those inmates away from the general population, but that didn't happen in this incident.
"The reason why we keep them separate is because usually they are concealing drugs or weapons," said Sidsworth. "My understanding is that this is what happened and that they were sharing medication of some sort."
Police would not confirm if the death is drug-related.
"There has been some suggestion that she may have ingested some narcotics in the jail," said Windsor Police Sgt. Matthew D'Asti. "We don't know what. We're investigating and waiting on toxicology results."
Blackbird is a 34-year-old woman who first made headlines in June when she was accused of stabbing a man on a transit bus in Windsor.
At the time, police said her boyfriend got into an argument with the victim on the bus. He was kicked off the bus and then ran to Blackbird. Witnesses say Blackbird got on the bus and allegedly stabbed the 23-year-old victim.
She was charged with assault with a weapon and was serving time in jail.
Police said they don't suspect foul play in Blackbird's death, but the investigation is ongoing.