The police response began Thursday night before midnight and followed a visit by military police to a house in Petawawa, home of the army's 2 Canadians Mechanized Brigade Group.
Military officials today confirmed military police were at the house Thursday night until the OPP arrived.
Typically military police only respond when incidents happen either on a military base or off-base and involve soldiers.
As of late Friday afternoon, the scene in the town about 1½ hours west of Ottawa was still under lockdown, with OPP tactical response unit officers deployed in camouflage uniforms and tactical vests and carrying assault rifles.
Pictures posted online show some officers wearing paint on their faces.
Residents told to stay indoors or stay away
CBC News has learned neighbours who live on the same street as the house have been asked to stay inside and to keep their children off the streets.
One resident, who is a soldier, told CBC News police are preventing him from going home.
"They won't let me into my house," the soldier said.
Although residents have not been asked to leave the neighbourhood, an evacuation centre has been set up at the Petawawa Civic Centre.
Police are urging residents of the affected neighbourhood not to go there.
However, in a news release Friday, the OPP said, "There is no concern for the safety of the public."
Still, neighbours say the police response Thursday night was substantial and included heavily armed officers and police dog teams.
Residents told CBC News on Friday they have seen tactical response unit officers hiding in bushes surrounding the neighbourhood.
Witnesses said there appeared to be more than two dozen officers on the scene and at least one armoured vehicle. Some officers have apparently come from as far away as Hawkesbury, Ont., 250 kilometres away.
The OPP have refused to release more details about the incident other than to say an investigation into a "matter" is underway.
In telephone calls with CBC News, residents said they have heard little from police about what is going on in their neighbourhood.
Officials at nearby Garrison Petawawa say none of their units is involved in the response to the stand off Friday.