Restricting access to all files?

Restricting access to all files?

For some reason, only the index.php file in my directory is being
restricted, even though I am using the following directives in the
.htaccess file:
AuthUserFile /path/to/.htpasswd
AuthName "Administration"
AuthType Basic
Require valid-user
Any idea why only the index.php page is being restricted? I can access any
other file in the directory without an authentication window.
Thanks!