'Misting' - i.e. condensation of the cooled air from the A/C vents is quite common here in the Middle East when on the ground with doors open and hot humid air from outside enters the cabin. (It's not really steam which implies it's been heated). Can be quite spectacular. I've also had fine dust articles picked up from a serious duststorm while taxi-ing later appear in the beams of the reading lights (night time take off) and cause alarm in some PAX. That also had a strange, but identifiably dusty, smell.
But misting (if that's what it was) would not account for the reported treatment for smoke inhalation and smell of kerosene in this incident.