Fire broke out on a subway train Saturday, filling attached cars with smoke and causing panic among passengers, police said. About 30 people were treated for smoke inhalation.

The conductor stopped the train after the fire broke out and passengers were led on foot through the smoky tunnel, said a duty officer at Milan's police office.

The blaze was caused by a short circuit in the locomotive engine, the duty officer said, speaking on condition of anonymity. It was promptly put out.