My experience with "Controle"

Here I would be writing about a true incident. I and my friend were walking down a busy crossing to buy some gifts for him to take back to his family. While waiting at the crossing to turn green I saw three police officers on the other side of the street. The signal turned green and we crossed but the moment we stepped on the other side these officers stopped both of us and asked if I spoke French. I said no and then they switched to better than bad english and told me they wanted to search me. I did not oppose thinking that I might have done something stupid and I was thoroughly searched. At the end of the search I asked the guy searching me if I did anything wrong, he simply said no its a "controle". I don't know what that means. I can only imagine a search like this without reason only when a country is under martial law but later I figured out that such searches are possible in France. The most strange thing that came to my mind is that at no point these officers demanded a proof of identity. They even asked a few times if I had money in my wallet? I had only coins but no euro bills. This incident happened on 21st January 2012 at around 5:30 pm on busy crossing in Grenoble. As an afterthought it came to me why did those guys only stop me and my friend and not anybody else from the crowd? A variety of explanations are possible and the most popular one in this scenario would have a pinch of color to the explanation. Many studies available on the internet do tilt the scale in favor of the color aspect but again how do I know what made those policemen to search me when these kind of searches are supposed to be random. May be this can be tested by using some random selection experiment. In a bucket if we place say lot colored balls of say red color and then put a few blue ones it would be interesting to note how often the blue ones are picked by a person looking at the bucket. I do not know what will be the result of such an experiment but it would be interesting to know. Anyway, the experience was not very pleasant but I hope it was truly a random event.