TCP/IP routing problem

I have a TCP/IP network that consists of seven segments in two
buildings connected using Routers and a T1 circuit. To alleviate
network congestion I have added a new segment in each building and
have moved 20 computers to each segment. I have checked the computers
and the Routers and they are configured correctly, but the new
segments can only see the existing segments, not each other. In
addition, none of the original segments can see the new segments in
the other building. The routing tables include the new segment
information in their building, but not in the other building. I can't
find the problem, please help.