Marked cards in a home game

[philr]

Last Friday i played in my regular home game. This was our first outdoor game of the season and we had 24 players - it was a really great night. However after the game was over and we were cleaning up we found that in one of the decks that was being used all of the 10's had a corner bent over. This was really a shock because this seems like someone is marking the cards.
What makes is worse is i had a small game earlier in the week and found a 10 with the corner bent but didn't think anything off it. This was in a deck i am not 100% sure if we used that night so it could have been used in any of the other previous games - i just cannot be sure.

So i have a few questions: Is someone marking cards? if so how do we smoke them out? What should we do once we find out who it is?

Thoughts suggestions and your experiences please.