"maven clean" triggers download of unrelated jar files

The job of the clean target is to delete a few files. It should not be necessary to download jcoverage and java-getopt, and the other jars are probably not too useful either. My project doesn't even use jcoverage...

For a user new to Maven (like me) this is confusing, I did not expect to start a download when I wanted to delete some files. It also takes much longer than necessary to execute the clean task (26s instead of 2s)

I should mention that this is a multiproject build, maven clean was executed on top level.

Here the console log of the build process (download artifacts compressed, path prefixes omitted)

clirr> maven clean
__ __

Attempting to download jcoverage-1.0.5.jar.
..
Attempting to download velocity-1.3.jar.
..
Attempting to download java-getopt-1.0.9.jar.
..
Attempting to download xpp3-1.1.2a.jar.
..
Attempting to download xercesImpl-2.4.0.jar.
..
Attempting to download xmlParserAPIs-2.2.1.jar.
..
build:start:

clean:clean:
[delete] Deleting directory .../clirr/target
[delete] Deleting: .../clirr/velocity.log
BUILD SUCCESSFUL
Total time: 26 seconds