An inmate of the Toronto South Detention Centre died Saturday after an apparent drug overdose, the Star has learned. It was the second prisoner death in a week at Ontario’s year-old superjail complex.

An official with the union that represents jail workers confirmed that on Valentine’s Day morning an inmate was rushed to hospital from the Toronto Intermittent Centre — a part of the Etobicoke jail that houses prisoners serving weekend sentences.

“It is believed the inmate died of a drug overdose,” said Monte Vieselmeyer, corrections division chair for the Ontario Public Service Employees Union.

The police, the Correctional Services ministry and the Ontario coroner’s office are investigating. “As such, it would be inappropriate to speak further on any specific details of the incident,” ministry spokeswoman Lauren Callighen said in an emailed statement.

On Thursday last week, another Toronto South inmate died in hospital two days after attempting suicide in his cell. His death is also under investigation, which is standard procedure in Ontario when people die while incarcerated.

The Toronto South was on lockdown for seven days beginning early last week after a series of violent incidents and security concerns, including the discovery that a set of jail master keys are missing. The keys have not been found, a source who spoke on condition of anonymity told the Star. The ministry wouldn’t comment on the keys.

The lockdown ended Monday, but “the institution re-entered a partial lockdown (Tuesday) due to staffing shortages and disruptive inmate behaviour,” Callighen said.

The ministry’s crisis intervention team was deployed after the “disruptive inmate behaviour,” which union officials said involved several inmates smashing glass cell windows that are supposed to be shatter-proof.

An inmate at the Hamilton Wentworth Detention Centre also died over the weekend of an apparent drug overdose, Vieselmeyer said, and two inmates at Maplehurst Correctional Centre in Milton overdosed last week but survived.

The Ontario Coroner’s Office is in the process of launching an inquest into four drug-related deaths at the Hamilton jail that occurred between 2012 and 2014, the Hamilton Spectator has reported.

Inmate drug smuggling is a lucrative business and an unfortunate reality of working in the correctional system, Vieselmeyer said. Drugs can be carried in through body cavities — ministry employees do not conduct full cavity searches — and sold at a high profit margin.

“The Ministry works very hard to remove and stop contraband from coming into our correctional facilities,” Callighen’s statement said.

“The Ministry’s most important priority is the health and safety of all our inmates and staff as we transform our corrections system both within and beyond the walls of our facilities. (The Toronto South) is an important part of this as a state-of-the-art direct and indirect supervision facility that will strengthen our rehabilitation and reintegration programs.”