Russian intelligence services are probably behind the explosion of shipments in courier warehouses in Europe in July, Polish prosecutors said, quoted by Reuters.
Western officials have previously said that Russia was trying to destabilize Ukraine's allies through sabotage. The explosions in courier warehouses in Great Britain, Germany and Poland could have caused more serious consequences.
Security officials said the shipments were part of a plot that ultimately aimed to detonate cargo flights to the US and Canada.
"The evidence collected in the case leads to the high probability that the discussed acts of sabotage were planned by the Russian special services," said the spokesman of the Polish prosecutor's office, Przemyslaw Nowak.
Nowak said Polish authorities are looking for two Russians and have detained four Ukrainian citizens as part of the investigation. Polish prosecutors said in October that they had detained four people and were looking for two others in connection with the shipments, but did not say what nationalities the accused were.
"We are working hard to identify the other persons involved in the above-mentioned international group," Novak said. "These actions are taken in cooperation with the law enforcement authorities of other countries of the European Union." He said the blasted packages were sent from the Lithuanian capital Vilnius.