Crystal Cave Ghost Pictures

"On me and my fiance's trip to Pennsylvania, we went to a place called Crystal Cave. The guide told us about the place, and it was discovered around 1800; a lot of people went through these caves. At one point, we were 150 feet below the earth as my fiance was taking pictures. We looked at the pictures on the digital camera to make sure they came out (I did not notice anything); but when I got the pictures developed, there seemed to be smoke in the pictures (there was no smoking in the caves so I'm not sure what it is but I thought it would be interesting to you). I believe in spirits...so they possibly could be ghosts."