[mod_python] installation problem: --prefix is ignored for Python libraries ?

We are using encap system in our production server, and I am trying to
upgrade to 3.3.1

I want to install Python libraries not in site-packages, but in
/usr/local/encap/mod_python-3.3.1
and then run encap, which would link them into site-packages. 
So I configure:

web10:/path/sys/src/mod_python-3.3.1 # ./configure
--prefix=/usr/local/encap/mod_python-3.3.1
--with-apxs=/usr/local/encap/httpd-2.2.6/bin/apxs
--with-python=/usr/local/bin/python --with-max-locks=64
#make
#make install
And it directly installs instead into
/usr/local/encap/Python-2.4.1/lib/python2.4/site-packages, ignoring my
configuration prefix:
"
.....
creating
/usr/local/encap/Python-2.4.1/lib/python2.4/site-packages/mod_python
copying build/lib.linux-x86_64-2.4/mod_python/Cookie.py ->
/usr/local/encap/Python-2.4.1/lib/python2.4/site-packages/mod_python
.....
"

How can I force it to install into /usr/local/encap/mod_python-3.3.1 and not
into site-packages?

Thanks.