NOTHING TO SEE HERE, MOVE ALONG: Russia Suspected of Plotting to Send Incendiary Devices on U.S.-Bound Planes.

Western security officials say they believe that two incendiary devices, shipped via DHL, were part of a covert Russian operation that ultimately aimed to start fires aboard cargo or passenger aircraft flying to the U.S. and Canada, as Moscow steps up a sabotage campaign against Washington and its allies.

The devices ignited at DHL logistics hubs in July, one in Leipzig, Germany, and another in Birmingham, England. The explosions set off a multinational race to find the culprits.

Now investigators and spy agencies in Europe have figured out how the devices—electric massagers implanted with a magnesium-based flammable substance—were made and concluded that they were part of a wider Russian plot, according to security officials and people familiar with the probe.

Security officials say the electric massagers, sent to the U.K. from Lithuania, appear to have been a test run to figure out how to get such incendiary devices aboard planes bound for North America.

Lithuanian police arrested a suspect who sent four incendiary devices, including two from a DHL shop in the capital Vilnius, a European law-enforcement official said. The suspect identified himself as Igor Prudnikov, but his real name is Alexander Suranovas, the official said. Investigators said they believe he was used as a proxy by Russian spy services.

Poland’s National Prosecutor’s Office said authorities there have arrested four people in connection with the fires and charged them with participating in sabotage or terrorist operations on behalf of a foreign intelligence agency.

Previously: Three guilty as court finds Russia-controlled group downed airliner.