Could be delivering liquid oxygen. Condensation dripping on the road. Overpressure relief blowing off a puff of cold gas. Did it have a diamond shaped hazmat sticker?
Do YOU want to take the chance that it's innocent? I wouldn't.
That was the weird thing. It looked like a medical van but no stickers on it anywhere. It was really new. As in 1 or two years old, was custom made, I have never seen a van exactly like it before. No Company slogan on the side, no hazmat stickers in the back. If the FBI wants to investigate it can. I did my part.
I guess I am profiling. But what are the odds that the van driven with the white cloud would have had a afghani or indian driver? But sometimes coincidences happen.