diff --git a/swh/loader/core/loader.py b/swh/loader/core/loader.py
--- a/swh/loader/core/loader.py
+++ b/swh/loader/core/loader.py
@@ -23,6 +23,7 @@
 from swh.loader.exception import NotFound
 from swh.loader.package.utils import download, get_url_body
 from swh.model import from_disk
+from swh.model.hashutil import hash_to_bytes
 from swh.model.model import (
     BaseContent,
     Content,
@@ -715,6 +716,7 @@
     def fetch_data(self) -> bool:
         """Retrieve the content file as a Content Object"""
         data: Optional[bytes] = None
+        expected_checksum = hash_to_bytes(self.expected_checksum.decode())
         for url in self.mirror_urls:
             url_ = urlparse(url)
             self.log.debug(
@@ -726,21 +728,22 @@
             )
             try:
                 data = get_url_body(url)
-                self.content = Content.from_data(data)
-
-                # Ensure content received matched the integrity field received
-                actual_checksum = self.content.get_hash(self.checksum_algo)
-                if actual_checksum == self.expected_checksum:
-                    # match, we have found our content to ingest, exit loop
-                    break
                 # otherwise continue
             except NotFound:
+                self.log.debug("Not found %s, continue on next mirror url if any", url)
                 continue
 
-        if not self.content:
-            raise NotFound(f"Unknown origin {self.origin.url}.")
+            content = Content.from_data(data)
+            # Ensure content received matched the integrity field received
+            if content.get_hash(self.checksum_algo) == expected_checksum:
+                # match, we have found our content to ingest
+                self.content = content
+                # we are done, no more data to fetch
+                return False
 
-        return False  # no more data to fetch
+        # If we reach this point, we did not find any proper content, consider the
+        # origin not found
+        raise NotFound(f"Unknown origin {self.origin.url}.")
 
     def process_data(self) -> bool:
         """Build the snapshot out of the Content retrieved."""