A fire that began Friday and has ravaged a St. Catharines, Ont., flower farm still isn't completely out, says the fire department.

Dave Upper, deputy chief of St. Catharines Fire and Emergency Services, told CBC News Sunday morning there is still active fire inside the greenhouse that's smouldering and producing smoke, but not active flames.

StC Fire Crews continue working on Seventh. Please avoid the area. <a href="https://t.co/GOj1jzfNIy">pic.twitter.com/GOj1jzfNIy</a> —@DaveUpper_ Upper said crews are going to start pulling the greenhouse apart to reach its core and get to the hot spots that have been trapped by a heavy concrete ceiling used for cold storage that has collapsed.

He said it will take the better part of Sunday to get all the hot spots out, but rain in the area will help.

The smoke on Saturday affected local air quality and officials from Ontario's Ministry of the Environment were on the scene, collecting air samples for analysis.

"Preliminary downwind air monitoring results are below emergency screening values," Andrew Buttigieg said in an email Saturday. "Local watersheds have been sampled and monitored. Early results show dissolved oxygen and pH readings being good."

Buttigieg said the city is collecting douse water that is being trucked to Port Dalhousie sewage treatment plant as a precaution.

No one was injured in the fire at Pioneer Flower Farms, although flames spread to and destroyed about four or five residential buildings that housed migrant workers, according to the acting fire chief for St. Catharines Fire and Emergency Management Services. (David Ritchie)

No one was injured in the fire at Pioneer Flower Farms that began late on Friday night, although flames spread to and destroyed about four or five residential buildings that housed migrant workers, according to Jeff McCormick, acting fire chief for St. Catharines Fire and Emergency Management Services.

The fire was in a structure of about 650,000 to 700,000 square feet in total that is a series of greenhouses and outbuildings.

The fire also spread across the grass and caused a "significant" bush fire, the city of St. Catharines said in a release.

Firefighters were called to the farm shortly after 11 p.m. ET, and crews from five departments were able to contain it after several hours.

Fire crews were working on hot spots Saturday afternoon, said Deputy Fire Chief Dave Upper in a tweet. (Dave Upper/Twitter)

Many people from the area, including neighbours, went to the farm to help. At one point, they set up an irrigation pipeline to bring water to one part of the fire.

Residents in the area northwest of the fire were asked to close doors and windows and turn off air conditioning. People are still being asked to avoid the area.

According to its website, Pioneer Flower Farms is a family business that started in 1971.