Migrating WordPress Blogs in subdirectory to WordPress Multisite

Folks,

We have three blogs in subdirectories as follows

http://xxx.com/blog1
http://xxx.com/blog2
http://xxx.com/blog3

As an effort to reduce maintenance issues and also interconnecting the blogs, we would like to make use of WordPress Multisite feature. But the pblm is say if we enable multisite in blog1 and migrate the other two blogs then their urls becomes http://xxx.com/blog1/blog2, http://xxx.com/blog1/blog3. But instead we want to retain the same urls (http://xxx.com/blog2, http://xxx.com/blog3) for obvious reasons.

Is there any possibility to do this. Thanks in advance.