Phil Larson of the White House office of science and technology policy, answered a question of a petition asking if the US Goverment is hiding any information about alien life.
And he answered:
"The U.S. government has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race, ... In addition, there is no credible information to suggest that any evidence is being hidden from the public's eye."
I must say that I have mixed feelings about this. Because I am happy that they are taking up this question, and actually give an answer, and this might be it - there are no secrets, they didn't collect anything from Roswell and such. And we are alone in the universe as far as we know.
But still I am not giving up hope and belief that there might be more out there than we know. And you also have to consider that it wouldn't be a good time for the US government to come out with such information right now, with all the problems they have and the already big insecurity worldwide. Saying "Hey btw guys, aliens exist!" wouldn't be a great idea, and probably not for a long time to come. But this is just my thoughts, and my small hope that there actually are more out there.