I've owned rats for 2 years; and it sounds like aggression caused by hormones and being excited. My girls get very excited when they're cage is cleaned, especially when there is a new addition in the cage. Rats have a certain pack order and males especially, as they are growing up and hitting that age will fight and be dominant. So, I wouldn't worry about the squeaking too much. They'll do plenty of it at this age when establishing dominance.
I suggest taking a look at
Rat Behavior and Biology, it really helped me understand my rats more. I printed the whole website out.