Winnipeg police are looking for a suspect in a stabbing that took place aboard a city transit bus on Saturday evening.

A 20-year-old man is in stable condition as a result of the stabbing, which took place sometime before 7 p.m. CT while the bus was near the Polo Park Shopping Centre.

Const. Jason Michalyshen said the victim and another 20-year-old man were on a Route 11 bus heading east on Portage Avenue when a third man approached them and a fight broke out in the back of the vehicle.

"The 20-year-old male that was not directly involved attempted to intervene once a knife was observed … and made every effort to break the two up," Michalyshen told reporters on Sunday.

The victim was stabbed during the altercation. The suspect ran off the bus and fled, according to police.

The two men also got off the bus and went to a home near Portage Avenue and Tylehurst Street, where police were called.

Michalyshen said it appears a relationship may have sparked the dispute.

"It appears that the two know each other as a result of a third party in a relationship that they both had — one who's currently involved in that relationship, one who had previously involved in that relationship," he said.

The stabbing victim is in stable condition and faces charges of breaching the conditions of a sentencing order.

Michalyshen said the suspect remains at large. Police will examine surveillance footage from the bus and rely on statements from the victim and witnesses, he said.

About 10 to 12 people had entered the bus at the same time as the suspect, Michalyshen said.

Tia Slotta, who takes the Route 11 bus regularly, said she and her son could have easily been on the same bus where Saturday's attack took place.

"Hearing about stuff like that, it does make me worry," Slotta told CBC News on Sunday.

"I could have been taking the bus with my son and something could have ended up happening to him."