Police said two masked suspects detonated a homemade improvised explosive device in Bombay Bhel restaurant.
Police said they received a call regarding the explosion, which occurred near Hurontario Street and Eglinton Avenue, just after 10:30pm, the report said.
"We transported three of them to trauma centres in what I would say is critical condition just from blast injuries", he said.
Other victims were treated for minor injuries after the blast at the eatery in a strip mall that is surrounded by houses, grassy fields, and condo towers under construction. Though Evans said children under the age of 10 were at one of the birthday parties, none of the children were hurt.
Two men are suspected of setting off an explosive device in the restaurant, with authorities asking for information about their identities and whereabouts.
Police stand outside the Bombay Bhel restaurant in Mississauga, Canada Friday May 25, 2018.More news: Daniel Ricciardo expects increased Ferrari, Mercedes threat
"The suspects fled in a auto and the police are looking for them over quite a wide area", he said.
Investigators are seeking the public's help in identifying these individuals.
The first suspect is described as a man in his mid-20s, between 5'10 and 6-feet with a stocky build and light skin.
Witnesses said the bomb looked like a paint can or a bucket and, according to police, was filled with projectile objects. No motive for the attack could be ascertained till now.
Three people were initially listed in critical condition, but by Friday morning their conditions had been upgraded to stable, Evans said.
Surveillance photos show the men wearing jeans and dark-colored hoodies.More news: Celtics brace for 'dogfight' vs Cavs in Game 7 at home
Evans said that police are still looking to track down a number of people who were at the restaurant but left the scene before police arrived.
New Democratic Party leader, Andrea Horwath, took to her Twitter page around 7:30 a.m. and said her thoughts were with the victims.
"We have no indication to call it a hate crime or any kind of terrorism act", Bertram said. The Consulate General of India has opened a helpline in the aftermath of the blast, a move which suggests numerous victims may be Indian citizens.
The area around the restaurant has been closed off with police cordons and emergency services present.
Andre Larrivee, who lives in a nearby condominium building, said he was watching television and heard an explosion.
The Plaza area around the restaurant has been sealed, The Express quoted the police as saying.More news: Relentless Ronaldo can break more Champions League records in final