Dozens of children were taken to hospital Tuesday after a carbon monoxide leak at a daycare northwest of Montreal.

Emergency officials responded to a 911 call Tuesday from Les Petits Explorateurs daycare located in St. Eustache, Que.

The entire daycare was evacuated after emergency crews detected a quantity of carbon monoxide. Approximately 10 educators and 72 children were taken to a local hospital, where a “code orange” was issued to make room for the influx of patients.

In most cases, the children and teachers were taken to the hospital as a precautionary measure, but officials said that at least two children were overcome by fumes and lost consciousness.

The daycare was first alerted to a problem when one child fell ill. Several children then reported headaches, but at least five had serious symptoms, such as vomiting.

Firefighters were called in when an ambulance technician who arrived on scene to treat the ill suspected carbon monoxide poisoning.

When firefighters arrived and confirmed the presence of carbon monoxide, the children and educators were transported to hospital by school buses and ambulance.

Hospital officials said that the children were treated quickly, and some will be released from hospital Tuesday afternoon. The five with more severe illness have been transferred to a pediatric hospital in Montreal for further evaluation and treatment.

However, none of the children or adults exposed to the carbon monoxide are in danger, health officials say.

“It was more by precaution and the other ones were fine, but they (were) treated with oxygen for six hours because this is the treatment that is usually done in those cases,” Dr. Marie-Claude Lacombe, of the Laurentian Regional Department of Public Health, told reporters.

Meanwhile, fire crews investigating the origin of the gas leak are looking at the possibility that a propane-fuelled machine that was used to polish the floors at the daycare the evening before may have malfunctioned and released the fumes.

At a news conference Tuesday afternoon, Quebec Minister of Families Francine Charbonneau said there will be an investigation into how the incident occurred in the first place.

“We don’t know what happened, so that’s why right now, there’s a team looking at everything that could’ve happened within the daycare and outside the daycare,” she said.

Charbonneau also said she’s waiting to hear if there were carbon monoxide detectors on site at the daycare.

A statement on the St. Eustache website said that the leak is “localized” and poses no risk to neighbouring buildings.

Carbon monoxide is a colourless, odourless gas. People affected by CO poisoning can suffer headaches, nausea and fatigue. Prolonged exposure can be fatal.

Prime Minister Stephen Harper expressed his wishes for a quick recovery on Twitter Tuesday: