Russian intelligence is suspected of being behind several "self-igniting" parcel fires around Europe, including one in Birmingham.
The Metropolitan Police said an investigation involving multiple countries was ongoing after "several fires involving cargo".
The fire at a DHL depot in Birmingham in July 2024 has been linked to other incidents on the continent.
A 38-year-old Romanian national was arrested in the UK last year on suspicion of assisting a foreign intelligence agency. He was released, but remains under investigation.
Deputy Assistant Commissioner Vicki Evans said Russian military intelligence is believed to be responsible.
Four parcels were sent from Lithuania to addresses in the UK and Poland in July 2024, a joint statement from European investigators revealed.
One caught fire in transit at Leipzig airport, where it was about to be loaded on to a plane, another exploded inside a truck in Poland, one was seized intact, and the other was the Birmingham incident.
"Test packages" were also sent to the US and Canada, while two more parcels bound for North America were intercepted in Amsterdam.
Twenty-two suspects have now been identified in Lithuania and Poland suspected of working on behalf of Russian military intelligence, according to Eurojust, the judicial arm of the EU.
The agency said the alleged perpetrators were recruited and given instructions through an online messaging service.
Investigators said tasks were divided among several suspects, who were often rewarded with cryptocurrency payments.
They came from various Slavic and Baltic nations, and were "often in a vulnerable socio-economic situation", according to Eurojust.
Two of them now face trial, with courts expected to hear their cases later this year.
All told, five nations - UK, Germany, Netherlands, Poland and Lithuania - took part in the investigation: .
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DAC Evans said: "The strength of cooperation in this case has led us to collectively identify what we believe to be Russian military intelligence involvement in a series of incidents across Europe.
"Our investigation is ongoing, and we continue to liaise closely with partners to ensure we're doing all we can to keep the sector, and the public safe.
"We have been clear and open about the increasing levels of demand we're seeing relating to the activity of foreign states here in the UK."
(c) Sky News 2026: Russian intelligence suspected after Birmingham targeted in 'self-igniting parcel' attacks
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