Two incendiary devices transported by DHL were part of a Russian plot to start fires on cargo or passenger planes headed to the US and Canada, the Wall Street Journal reports.

The current plot shows an escalation of previous suspected attacks in July when devices set fires at DHL logistics hubs in England and Germany.

Since the incidents in July, security officials have been searching to find the culprit and have now determined that Russia was behind the planting of incendiary devices, according to the Wall Street Journal.