Police are looking for four suspects after a stabbing on the first day of class at Central Technical School put one student in hospital, and others in lockdown for three hours. 

The 19-year-old male student suffered a collapsed lung after he was stabbed "in the chest and side," at about 1 p.m. on Tuesday, according to Det. Jessica McInnis of 14 Division. 

'This could have been much worse.' — Det. Jessica McInnis, 14 Division 

​McInnis said the victim was stabbed when an argument between two groups of people, composed partly of Central Tech students, turned violent. The incident occurred on school property, but not in the building. 

"This was not a random act," McInnis told reporters. "Parents shouldn't be worried." 

Investigators zeroed in on the suspects after reviewing video evidence, she said. 

"We have several outstanding suspects. We've ID'd a few of them. We'd like them to speak to their parents, speak to a lawyer and turn themselves in to 14 Division right away." 

The suspects are all male, but no descriptions have been released because their ages are not known. It is also not known if any of them are students. 

Victim arrested

McInnis added that the victim, who was still in surgery by late afternoon, has also been arrested on a separate matter, but would not give more details. 

Police recovered two knives from the area; one from school property, the other from a nearby sewer. 

The school, which is on Bathurst Street near Harbord in downtown Toronto, was locked down until 4 p.m. 

Some witnesses said the victim was trying to break up the fight when he was stabbed.

School principal Lisa Edwards told reporters the victim came onto school property after he was stabbed, and was assisted by students and three teachers. 

"The students were very concerned at the time," Edwards said. "This is a very positive school community. The students watch out for each other."

McInnis applauded the school's safety efforts. 

"The school really, really did a great job. This could have been much worse."