Toronto police have issued a public safety alert.
They say a number of suspected overdoses, including one fatality, may all be connected to the same drug.
Police were called to the Uniun nightclub on Adelaide St. in the Entertainment District around 12:42 a.m. Saturday where they found two people in medical distress.
One of those people, a 24-year-old woman, died.
They were also called to The Rebel nightclub on Polson St at 1:30 a.m.
They found three people suffering from suspected drug overdoses.
Police say all of them may have taken the drug MDMA which is also known as ecstasy.
Along with death, the illegal substance can cause addiction, kidney damage and memory loss.