GATINEAU, Que. - 21 Gatineau kids are in Hospital after reports of strange fumes aboard their school bus.

The children attend Ecole Saint-Jean Bosco in Gatineau, reporting symptoms of headaches and nausea.

Five ambulances were dispatched to the scene at 10 a.m., paramedics say.

Gatineau Police were looking at the possibility of the source might be carbon monoxide, but Commission Scolaire des Portages-de-l'Outaouais ruled that out as a cause. The school board says it was a mechanical issue on the bus.

A total of 43 children were assessed, half of whom did not need to go to hospital. 

None of the symptoms are reported to be severe.

"By the time I got here, the doctor said she was fine," said parent Sean Horne.

"Anytime you get a all like there, there's always uncertainty, and you're scared."

His daughter is in grade 3 at Saint-Jean Bosco, and had a sore stomach, but was okay.

17 children have been sent to hospital in Gatineau sector, 4 other have been sent to Hull. The children have been sent to hospital as a precautionary measure.

Gatineau Police are investigating and say while these incidents are rare, they do happen.

The school board says all the kids were fine and had been discharged from the hospital by 3 p.m. Friday.