"I find it hard to believe that nobody in your government knows where they are and couldn't get them if they really wanted to," The Daily Times quoted Clinton, as saying.
"Maybe that's the case; maybe they're not gettable. I don't know... As far as we know, they are in Pakistan," Clinton told mediapersons here.
She said Pakistan is facing numerous problems and with such a large population to feed the issue has only aggravated.
Clinton stressed that Islamabad must tackle problems related to its ever increasing population.
"You do have 180 million people. Your population is projected to be about 300 million. And, I don't know what you're going to do with that kind of challenge, unless you start planning right now," Clinton said.
Clinton also met Chief of Army Staff General Ashfaq Pervez Kayani at the General Headquarters (GHQ) in Rawalpindi and exchanged views on a host of security-related issues.