Russia’s FSB security service announced today that it has arrested a group of former defense industry workers suspected of supplying Ukraine with sensitive military information and planning sabotage attacks.

The FSB accused the unnamed former employees of spying for Ukraine’s military intelligence services and delivering technical documents and models used in the manufacture of weapons systems and equipment for Russia’s air force.

It said in a statement that the same group was also involved in plans to blow up transport infrastructure, such as railway lines used to supply Russian forces fighting in Ukraine.

The FSB said it had launched investigations into the former employees, on charges of treason against the country and preparing acts of sabotage.

“The suspects have been taken into custody and are proceeding with confessions,” the FSB said.

“Plastic explosives with a total mass of more than 4 kilograms, four detonators, manuals of military plans and materials used for military purposes as well as $150,000 were seized,” the statement said.