Police here said that two suspects detonated the improvised explosive device in the restaurant and fled.
According to the Canadian broadcaster CP24, emergency crews responded to the area of Hurontario Street and Eglinton Avenue at around 10:30 p.m.
"We transported three of them to trauma centres in what I would say is critical condition just from blast injuries", he said. Images from a photographer on the scene show families, including children, outside the restaurant when ambulances and police cars had arrived.
"The men were seen fleeing the scene immediately following the explosion".
The incident occurred in the restaurant called Bombay Bhel.
Police in a Toronto suburb are searching for two masked attackers who detonated an improvised bomb in a restaurant Thursday night.
Peel Regional Police investigating the blast tweeted about the powerful explosions. "Certainly, the people who have done this need to answer for their crimes, and they need to be brought to justice".
No group has claimed responsibility for the attack and the motive is not known.
Twelve of the injured had been released from the hospital by Friday morning, Evans said. His face was covered with black cloth material. Some 15 people were taken to the hospital after the blast at the Bombay Bhel restaurant.
"Nothing was said by these individuals", Peel Region Sergeant Matt Bertram said.
The blast happened as at least two separate birthday parties were taking place.
The second suspect is understood to be a little shorter, fair skinned, of thin build and was wearing faded blue jeans, a dark zip-up hoodie with the hood also pulled over his head, a grey t-shirt, dark coloured skate shoes and his face was covered as well.
Bertram said police sealed off a couple of areas east of the restaurant where footprints, a glove and other evidence were located.
"There's no indication this is a terrorist act, no indication this is a hate crime at this time", Peel Police Chief Jennifer Evans told reporters Friday.
"I am in constant touch with our Consul General in Toronto and Indian High Commissioner in Canada", Swaraj said in a tweet.
Canadian broadcaster CBC reported a heavy police presence, complete with "tactical teams" - and said an officer on the scene could not say whether there was a further threat to public safety.
Andre Larrivee, a witness at the explosion, told Globe and Mail newspaper: "It was really loud".