Builds stuck in the queue

Hi,

We are facing a critical issue (live environment) where we are unable to perform any build in TFS (2013 update 2). All the builds are getting stuck.

We did following 

1. Restarted the build service on the servers, No go
2. Stopped and deleted the current running builds
3. Queued the new builds, and still same issue
4. Ran the build pointing to the other server, No go
5. Searched in the event viewer of build servers and app servers, nothing found
6. We tried restarting the build servers also but no luck the issues still persist

Could some one please help me as this is a production issue and which is impacting live environment.

please let us know if you need more details.

Thanks in Advance!

Thanks, BEshwar