diff --git a/swh/loader/npm/client.py b/swh/loader/npm/client.py
--- a/swh/loader/npm/client.py
+++ b/swh/loader/npm/client.py
@@ -138,11 +138,11 @@
             tarball_request = self._request(tarball_url,
                                             throw_error=False)
             if tarball_request.status_code == 404:
-                self.log.debug('Tarball url %s returns a 404 error.' %
+                self.log.debug('Tarball url %s returns a 404 error.',
                                tarball_url)
                 self.log.debug(('Version %s of %s package will be missing and '
-                                'the visit will be marked as partial.') %
-                               (version[0], self.package))
+                                'the visit will be marked as partial.'),
+                               version[0], self.package)
                 continue
             version_data = self.package_metadata['versions'][version[0]]
             yield self._prepare_package_version(package_source_data,
@@ -150,14 +150,13 @@
 
     def _prepare_package_version(self, package_source_data, version_data):
         version = version_data['version']
-        self.log.debug('Processing version %s for npm package %s' %
-                       (version, self.package))
+        self.log.debug('Processing version %s for npm package %s',
+                       version, self.package)
 
         # create temp dir to download and extract package tarball
         path = os.path.join(self.temp_dir, version)
         os.makedirs(path, exist_ok=True)
         filepath = os.path.join(path, package_source_data['filename'])
-        self.log.debug('Package local path: %s' % filepath)
 
         # download tarball
         url = package_source_data['url']
@@ -181,6 +180,9 @@
         # uncompress tarball
         tarball.uncompress(filepath, path)
 
+        # remove tarball
+        os.remove(filepath)
+
         # do not archive useless tarball root directory
         package_path = os.path.join(path, 'package')
         # some old packages use their name as root directory
@@ -192,6 +194,8 @@
         if not os.path.exists(package_path):
             package_path = path
 
+        self.log.debug('Package local path: %s', package_path)
+
         package_source_data.update(hashes)
 
         # parse package.json file to add its content to revision metadata
diff --git a/swh/loader/npm/loader.py b/swh/loader/npm/loader.py
--- a/swh/loader/npm/loader.py
+++ b/swh/loader/npm/loader.py
@@ -55,7 +55,7 @@
         in mid-air (OOM killed), we try and clean up dangling files.
         """
         if self.debug:
-            self.log.warning('DEBUG: will not pre-clean up temp dir %s' %
+            self.log.warning('DEBUG: will not pre-clean up temp dir %s',
                              self.temp_directory)
             return
         clean_dangling_folders(self.config['temp_directory'],
@@ -68,11 +68,11 @@
         npm source package tarballs.
         """
         if self.debug:
-            self.log.warning('DEBUG: will not clean up temp dir %s' %
+            self.log.warning('DEBUG: will not clean up temp dir %s',
                              self.temp_directory)
             return
         if os.path.exists(self.temp_directory):
-            self.log.debug('Clean up %s' % self.temp_directory)
+            self.log.debug('Clean up %s', self.temp_directory)
             shutil.rmtree(self.temp_directory)
 
     def load(self, package_name, package_url=None,
@@ -244,6 +244,9 @@
                        package_source_data['sha1'])
         self.known_versions[package_key] = revision['id']
 
+        self.log.debug('Removing unpacked package files at %s', dir_path)
+        shutil.rmtree(dir_path)
+
         return not self.done
 
     def _target_from_version(self, version, sha1):