MONTREAL — At least a dozen elementary school students were taken to hospital, and three older students were arrested, after a smoke bomb was thrown into a schoolyard Friday afternoon.

Police were called to the elementary school in Rawdon, north of Montreal, after students were incapacitated by the smoke, said provincial police spokeswoman Martine Isabelle.

Several ambulances arrived to transport children to hospital while others were taken there by their parents.

“The police intervened quickly and found the three suspects who are currently being interrogated,” said Isabelle.

“They are students from another school...the suspects are teenagers.”

The victims are all said to be in stable condition. The motive for the attack is not clear.

Rawdon is 75 km north of Montreal.