TORONTO, Ont. – Five children were taken to hospital after falling sick at the Art Gallery of Ontario Friday morning.

The children, aged 11 to 12, were taken to hospital with flu-like symptoms after the five children complained of nausea and one child fainted.

The children were visiting the “Frida and Diego” exhibit at the gallery.

A hazardous materials team tested the air but did not find any harmful substances.

“As the safety of visitors and staff is the AGO’s top priority, the exhibition space was immediately cleared and environmental conditions were fully assessed,” the AGO said in a statement.

“Testing confirmed that the Gallery’s air quality is excellent throughout the building, and shortly thereafter the exhibition was re-opened.”

Emergency officials speculate the children might have inhaled exhaust fumes likely from an idling bus or construction equipment on their walk from the subway to the gallery.

“We’re trying to figure out where they came from, what route they would have taken, what they may have encountered along the way,” Sgt. Ian McLaughlin said.

“It was only a small portion of the children that were affected.”

The children are expected to be OK.

A woman also fell sick at the AGO in an unrelated incident on Friday.