The search for two young men believed to be behind a shooting that wounded three people in a small southern Ontario city stretched into a second day on Friday as investigators worked to identify the suspects.

Niagara regional police Const. Phil Gavin said that while investigators have released most previously cordoned-off areas related to the incident in St. Catharines, Ont., those allegedly responsible for the violence were still at large.

"We've scaled back in terms of the active scene," Gavin told The Canadian Press in an interview. "What we'll probably get into at this point is the investigative side of things, where we'll be canvassing for information."

The shooting erupted shortly before 4 p.m. on Thursday in a downtown neighbourhood that a local politician described as "economically depressed."

Police suggested there were multiple scenes of activity and later described the incident as targeted. They have said they're looking for two men between the ages of 19 and 23 who were wearing hoodies and jeans.

Two of those injured in the gunfire were transported out of the city with life-threatening injuries, while the third was treated in a local hospital for what were considered less serious wounds, police said.

Gavin said Friday that he did not have any updated information on the conditions of the injured, and their names have not been released.

Police had planned to keep investigators at three scenes overnight -- the original site of the shooting and two nearby homes. Gavin said investigators have since been able to concentrate on one residence with suspected ties to the men being sought.

"(We) cleared the residence, and that residence is currently being held pending a search warrant," Gavin said.

The investigation had shut down local streets and kept residents out of their homes for several hours while police combed the area. Gavin said all public areas tied to the police probe are once again accessible.

Earlier on Friday, Police Chief Bryan MacCulloch sent a series of tweets acknowledging the effect such incidents can have on the city.

"We understand that an incident of this nature impacts our entire community," he wrote. "Our officers are continuing their efforts to investigate this matter fully and pursue all leads to identify the suspects involved and bring a peaceful resolution."

MacCulloch added that he was grateful to all those involved in the "complex and dynamic" shooting investigation.

Coun. Mat Siscoe, who represents part of the area where the shooting took place, said the neighbourhood has struggled economically in recent years. But he said such levels of violence are unusual.

"We're not used to gun violence in the city," he said. "Not on this scale."