Two people have died and more than a dozen others have fallen ill after they ingested what police believe to be drugs purchased at a music festival in Toronto this weekend.

At a news conference Monday evening, Toronto police deputy chief Mark Saunders said that 15 people in a state of medical distress have been hospitalized since Sunday night.

"Out of the 15, two have succumbed and died as a result of ingesting what we believe to be party drugs which were purchased at the Veld Music Festival," he said.

Saunders said that a 20-year-old woman and a 22-year-old man have died.

The deputy chief said that a 16-year-old was among those who fell ill. The average age of those affected is 19, he said.

The Veld Music Festival was held at Toronto's Downsview Park over the weekend. The two-day event had a lineup that included Dutch DJ Armin van Buuren, Scottish DJ Calvin Harris and Australian hip-hop performer Iggy Azalea.

Saunders urged members of the public to ensure that any loved ones who attended the music festival seek any needed medical attention.

"If anyone you know was at that festival and you have concerns for their behaviour or how they are acting right now, or if they are in any kind of distress, it is important that they go to the hospital immediately and seek medical attention," he said.

People are saying it could be MDMA, it could be ecstasy, it could be GHB. - Toronto police Deputy Chief Mark Saunders

Police are urging concertgoers to turn over any drugs they purchased to investigators.

Saunders did not have information on the types of drugs that had caused the illness and deaths.

"People are saying it could be MDMA, it could be ecstasy, it could be GHB," he said.

MDMA is a euphoric drug commonly known as ecstasy that has for decades been part of rave, club and other party scenes around the world. GHB is often referred to as the date-rape drug because it can cause drowsiness, unconsciousness and amnesia and has in some cases been used to make victims of rape docile. (Both names are abbreviations of the chemical compound of which the drugs are made.)

Saunders said police are confident that a substance ingested by people attending the music festival is related to the fatalities.

"People are dying because they are ingesting this drug," Saunders said. "We want to find that drug, we want to find out exactly what it is."

He said police would have more information to release on Tuesday regarding "the methods of ingestion."

The homicide squad is leading the investigation into the deaths.