Italian authorities say a bus driver transporting schoolchildren stopped his vehicle on a provincial highway, told the passengers to get off and then doused the interior with gasoline and set it on fire.

Italian media reported that the driver, an Italian of Senegalese origin, was immediately apprehended. The motive for the arson attack Thursday morning on the outskirts of Milan was unclear.

An official told Sky TG24 that the middle school-age children alerted authorities, aiding a speedy emergency response. Twelve children and two adults were taken the hospital but authorities reported only one injury.

Video showed firefighters dousing the bus that had been completely gutted by flames, leaving only the charred metal frame. ANSA said the bus was carrying about 50 children from the Lombard province of Cremona.