Resolution:
In order to delete the bridge, you need to use the delete bridge command in Administration Tool as follows:

delete bridge       source=&lttype>:&ltname> target=&lttype>:&ltname>

If target destination does not exist,  you will encounter "Bridge not found" error when attempting to
delete a bridge with the tibemsadmin utility.  Though show bridge shows the bridge details, need
target to delete it. Otherwise, it will give this error. This is an expected behavior only.