How to remove specific file types (i.e. docx) from multiple specific Sharepoint libaries using Powershell?

I am a newbie when it comes to Powershell so I'm asking for help. In Sharepoint 2010 I have several document libraries in a single site collection that all start with the name of 'PT-' and in those libraries are specific files that I need to delete like *.xyz. How can I loop through the libraries and remove the files based on the file extension using Powershell?

Any help would be appreciated and let me know if I need to supply more information.

Thanks, Mike