Research faculty I would like to work with not in my department I'm currently in the process of applying to graduate schools for admission into a graduate program in Computer Science. However, in a particular university that I would like to apply to, labs dealing with the specialization that I would like to work with belong to another department in the university and do not seem to involve faculty in the Computer Science department.

Now, when I write my Statement of Purpose for an admission into the Computer Science department, would it be considerate for me to mention my interest in working with these faculty outside the Computer Science department or must I restrict myself to those faculty and research labs under the purview of the Computer Science department in that university?

Is it possible even for me to be denied an admission if these faculty I'd like to work with and mention about in my statement do not belong to the Computer Science department?
Yes, it can hurt your chances of admission if your application focuses on a desire to work with people in a different department.  It's fine if you list some people in other departments, for example if they collaborate frequently with members of the department you're applying to (or even if they don't, provided they aren't the sole focus of your application).  However, you don't want to submit an application that looks like it's a substantially better fit for another department.  You might still get admitted if your application is strong enough, but there's a real risk someone on the admissions committee will try to make room for another candidate by declaring that you really belong in the other department.

This generally isn't a problem if you take it into account while planning.  If the best advisors for you are all in applied math or operations research, say, then you can apply to those departments in addition to computer science.  The only tricky case is if your advisor works on two very different things, one of which falls into the other department while the other is more traditional computer science, and you want to do the latter.  In that case you should explain in your statement of purpose why the computer science department would be a better place for you despite your choice of advisor.