Police are still working to track down the two men suspected of detonating a nail bomb in an Indian restaurant in Toronto on Thursday night.

The men were seen entering the Bombay Bhel restaurant with their faces covered just after 10.30pm. They set down their bomb - which appeared to be a paint can or pail - in the reception area, turned and ran away as it detonated.

Only two groups remained in the restaurant - one group, sitting at the front of the restaurant, had been celebrating a young boy's birthday, the National Post reported.

Police are still searching for two white men suspected of bombing an Indian restaurant (pictured) in Mississauga, near Toronto

Police say 40 people were still in the restaurant when the bomb detonated, including one group celebrating a young boy's birthday

Of the 15 injured, three were critically wounded, but all victims were released from hospital by Friday

A child is pictured being carried to safety after the frightening blast

Following the blast, witness Rafael Conceicao described utter chaos.

'Everything was destroyed. Lots of blood in the floor,' he told The Star. 'Many people were screaming. They were trying to run out from the restaurant.'

While 40 people were inside at the time, only 15 were injured. Three of them were in a critical condition, but all of them are now stable.

The most seriously wounded were a 35-year-old Brampton man, a 48-year-old Mississauga woman and a 62-year-old Mississauga woman. It is not known if the trio were all at the same table.

Raj Sapkota, a waiter at the restaurant, told The National Post he saw 'so many nails' after the blast.

He said one person, who he believed was the birthday boy's father, was bleeding from his stomach.

'He was the most injured,' he said.

Sapkota said the bomb shattered glass doors and tore apart the ceiling.

He said people were crying and shouting as blood pooled around them, and while the blast left very little smoke, the stench of gasoline filled the room.

A waiter at Bombay Bhel said he saw 'so many nails' after the blast, and said the man who was most badly injured appeared to be the birthday boy's father

The most seriously wounded were a 35-year-old Brampton man, a 48-year-old Mississauga woman and a 62-year-old Mississauga woman. It is not known if the trio were all at the same table

One witness said 'everything was destroyed' in the blast and there was 'lots of blood in the floor'

Blast: The incident took place in Mississauga, a city near Toronto in Ontario

The first of the two men seen bringing the bomb into the restaurant is described as being in his mid 20's and five-foot-10 to six feet tall. He had light skin and a stocky build, and on Thursday night was wearing dark blue jeans with a dark zip-up hooded jacket.

He also wore a baseball cap with a light grey peak.

The second man is between five-foot-nine and five-foot-10. He is pale skinned and thin.

On the night, he wore faded faded blue jeans, a dark zip-up hooded jacket with a grey T-shirt and dark-coloured skate shoes.

As of Friday afternoon, police had finished examining the areas surrounding Bombay Bhel, but officers had not set foot inside.

Police are waiting for a search warrant to be approved by the court. Though in an active crime scene, a warrant is not required, police spokesman Sergeant Matt Bertram told the National Post police were being cautious.

'We're going to play it safe, do everything we can, to make sure we're not going to lose this case based on the technicality of a warrant, and to give us proper judicial authorization to enter there and collect evidence,' he said.

The explosion also shattered a set of glass doors and blew a hole in the ceiling, a witness said

Police had not entered the restaurant as of Friday afternoon as they waited for a court to approve a search warrant

On Thursday, dozens of emergency crews were seen outside the restaurant in Mississauga, Canada's sixth largest city, about 20 miles west of Toronto.

Local police said the bomb was filled with 'projectable objects', and added they had 'no indication to call it a hate crime or any kind of terrorism act' at this stage of the investigation.

Mississauga Mayor Bonnie Crombie said she was thankful there were no fatalities.

'I would call it a very heinous, reprehensible act committed by cowards who came into a restaurant where people are vulnerable, celebrating with their families and where children are present,' she said.

'This is certainly not anything you would expect to happen in Mississauga, not my Mississauga. This is not the Mississauga I know.'