Local Nexus Repository Acting Like A Proxy For Some Maven Artifacts

Local Nexus Repository Acting Like A Proxy For Some Maven Artifacts

I am using my own version of the Nexus web app repository installed on my
local machine. I have Nexus configured with only one repository, the one
where I store my snapshots:
http://localhost:8081/nexus/content/repositories/MySnapshots/
Note that after the Nexus installation I removed all the default
repositories and added just my own. (Perhaps this was a bad idea?)
When I do a mvn clean install I noticed that some of the 3rd party
artifacts are downloading straight from the remote repository. For
example, here is one of the output lines from the build:
Downloading:
http://repo.maven.apache.org/maven2/com/sun/org/apache/xml/internal/resolver/...
The strange thing is that I see other artifacts are going through my local
Nexus to ultimately get to the artifact:
Downloading:
http://localhost:8081/nexus/content/repositories/MySnapshots/org/apache/maven/wagon/wagon-provider-api...
Notice how the first part of the download url is my local repository but
everything after MySnapshots is from apache.org.
It's almost like my Nexus repository is acting like a proxy to
maven.apache.org for some artifact downloads but for others it goes
straight to the source.
Can anyone tell me why this is happening?
I would't be bothered so much by this if all my builds succeeded all the
time but sometimes, when I am compile large projects, I get build failures
due to not being able to find an artifact.
If you would like to see my settings.xml for Maven and my pom file for the
project I am building when I see this you can view them here:
settings.xml: http://pastebin.com/NvLr5bEA
pom.xml: http://pastebin.com/PJ0P3RaK