Fifteen people injured in an explosion inside an Indian restaurant in Mississauga, Ont. have been released from hospital as police continue to search for two masked men who fled the scene.

Police have not made any arrests in connection with the blast at Bombay Bhel restaurant late on Thursday. Three people suffered critical injuries in the blast, and 12 others sustained smaller shrapnel injuries.

Both the mayor of Mississauga and the city’s chief of police say the investigation is in its infancy, and they have no reason to believe the attack was a hate crime or an act of terrorism.

Two masked men entered the restaurant in central Mississauga just after 10:30 p.m. Thursday and detonated an improvised explosive device before fleeing into a nearby residential area, police said. Police believe the men then drove off in a vehicle.

Witnesses said the blast could be heard from four blocks away.

Two separate birthday parties were underway at the time. Several children under the age of 10 were inside the restaurant, but none were injured.

Those most seriously injured included a 35-year-old Brampton man, a 48-year-old Mississauga woman and a 62-year-old Mississauga woman.

All 15 victims were taken to hospital and treated. The three people hurt worst in the blast were the last to be released on Friday.

Police released a photo of the two masked men entering the restaurant. One suspect is described as being in his mid-20s, with light-coloured skin and a stocky build, wearing dark blue jeans and a baseball cap with light grey peak.

The second has fair skin with a thin build and was wearing faded jeans, a grey T-shirt with dark-coloured skate shoes.

Police officers scoured a neighbourhood just east of the restaurant on Friday. In one area, investigators took measurements of what appeared to be footprints in a patch of dirt. Police also found two gloves on the sidewalk and took them as evidence.

Officers spent part of the morning knocking on doors and asking residents for any surveillance video they may have of the suspects.

Closer to the plaza, investigators were seen combing a grassy area behind the restaurant in search of clues.

Mayor: ‘A heinous act’

The motive behind the attack remains unclear. Peel Regional Police Chief Jennifer Evans said there is no indication of terrorism, but nothing has been ruled out.

“Every police resource is being used right now to identify those responsible for this horrendous act,” Evans said.

Mississauga Mayor Bonnie Crombie called the bombing “senseless.”

“I would call it a very heinous reprehensible act committed by cowards who would come into a restaurant where people are vulnerable, celebrating with their families, where children are present, and set off an IED. It’s a heinous act,” she told reporters outside the restaurant.

Crombie said she believes her city is still one of the safest in Canada, and that this was an “isolated” incident.

Police initially entered the restaurant to search for other explosives and for any other victims. None were found. They are now waiting to obtain a search warrant to conduct a full investigation of the scene.

Police are looking to track down several people who were at the restaurant but left before police arrived.

"This is a really serious investigation," Evans said told reporters early Friday morning. "We want to take our time, make sure we're very methodical in it. So we're putting a lot of resources into this right now."

Crombie said she has heard from Prime Minister Justin Trudeau, Premier Kathleen Wynne and Toronto Mayor John Tory, all of whom offered their condolences and support.

Determining a motive

Public Safety Minister Ralph Goodale also asserted that there is no information suggesting that the blast was a hate crime or related to “national security.”

“It’s far too early to draw any conclusion about what the motivation was here,” Goodale said Friday.

Goodale said he was pleased to learn that the victims’ conditions have improved, and he praised police officers in Mississauga.

“Canada is very fortunate to be one of the safest countries in the world, and our police services do an extraordinary job in making sure that’s the case.”

It’s always difficult to determine a link to terrorism or a hate crime, according to CTV News safety analyst Chris Lewis.

“If it’s terrorism, of course, it has to be related to religion or politics,” Lewis told CTV News Channel on Friday.

“With hate crimes comes certain observations, certain things said, certain things done, certain behavioural aspects that would indicate there’s an element of hate involved. They’re obviously not seeing any of that.”

The next steps for police, Lewis said, is assessing the remains of the explosive for any signs of DNA or fingerprints that could pinpoint a suspect. Investigators will also want to interview restaurant-goers to determine if an individual or group may have been targeted.

Lewis suggested that, because no one was killed in the blast, the bomb may have been “crudely made” and not intended to cause fatalities.

“One other option of course – there may be lots – is that they weren’t intending to totally destroy the building and kill everybody, just make a statement of some sort, particularly if you’re dealing with organized crime, someone trying to send a message to a rival or whatever that ‘don’t mess with us.’”

The Mississauga restaurant is part of a chain. The company released a statement on its Facebook page on Friday morning, calling the incident “extremely horrific and sad.” The location will be closed until further notice.

The Ontario Provincial Police and police agencies in Toronto, York and Halton have been asked to be on the lookout for the two suspects.

Police are also asking nearby residents to check surveillance camera video in hopes that police can identify any getaway vehicle the two men might have used.

The Indian consulate in Toronto has opened a helpline for any Indian nationals seeking assistance: (647) 668-4108.

Update #Mississaugaexplosion - police now say ALL of the injured in the #ied attack have been treated an released. Yesterday they said 3 were in critical, then stable. @CTVNews — Peter Akman (@PeterAkman) May 25, 2018

Taking down some of the police tape around the #MississaugaBombing restaurant- reopening part of the strip mall back to shoppers. The search for the two men who left the #IED continues. @CTVNews pic.twitter.com/SLkoS6e64J — Peter Akman (@PeterAkman) May 25, 2018

Police searching the brush behind #Mississaugaexplosion restaurant. Witnesses say the two masked men set off an #ied then ran this way before taking off in a vehicle. @CTVNews pic.twitter.com/mODZrc5Yuy — Peter Akman (@PeterAkman) May 25, 2018

Police say it’s was an #IED that injured 15 in this #Mississauga restaurant. But despite the explosion which witnesses say they heard 4-blocks away - none of the outside windows have been shattered. #Mississaugaexplosion @CTVNews pic.twitter.com/1IxTWJf36Z — Peter Akman (@PeterAkman) May 25, 2018

The Consulate General of India in Toronto has opened a helpline in view of the explosion at an Indian restaurant in Mississauga. For any assistance, pl call +1-647-668-4108. — IndiainToronto (@IndiainToronto) May 25, 2018

We're in solidarity with the victims of this violence, and wish a swift recovery to the injured. We’re working closely with police and officials in Mississauga on this. https://t.co/AQBuFZPXNY — Justin Trudeau (@JustinTrudeau) May 25, 2018

We are all shocked and saddened by the news out of Mississauga. Our thoughts are with the victims and their families, and our thanks go out to the first responders. We are monitoring the situation and I will be briefed first thing this morning. — Kathleen Wynne (@Kathleen_Wynne) May 25, 2018

This is not our #Mississauga. Thankfully there were not any fatalities and none of the victims were children. I’m calling on the perpetrators to turn themselves in. If you have any information, please call Peel Police. @PeelPoliceMedia will provide updates throughout the day. pic.twitter.com/U0pC4FbAZT — Bonnie Crombie (@BonnieCrombie) May 25, 2018

2 suspects attended the scene, detonated an Improvised Explosive Device within the restaurant. Several injured were taken to local hospital and 3 in critical condition were taken to a Toronto Trauma Centre. pic.twitter.com/yzCT59UVN6 — Peel Regional Police (@PeelPoliceMedia) May 25, 2018