Three people were arrested in Spain and one more in Germany on suspicion of belonging to a network that supplied the Lebanese militant group Hezbollah with parts to build kamikaze drones that would have been used in attacks in northern Israel, Spanish authorities said Thursday.

The investigation began in Spain when the Guardia Civil detected “suspicious operations” by Spanish companies run by Lebanese nationals involving large quantities of materials and components to manufacture drones capable of carrying explosive charges of several kilograms, the statement said.

Authorities believe Hezbollah may have built several hundred drones with these components.

The Spanish companies, as others in Europe and around the world, purchased items including electronic guidance components, propulsion propellers, gasoline engines, more than 200 electric motors and materials for the fuselage, wings and other drone parts, according to investigators.

The parts acquired by the network, which has now been dismantled, were identified in drones used by Hezbollah militants in attacks against Israel after the start of the Gaza war, which was triggered by the Hamas attack on Israel on Oct. 7.

Since then, Israeli air strikes on Lebanon have killed more than 450 people, mostly Hezbollah fighters, but also more than 80 civilians and non-combatants. On the Israeli side, 21 soldiers and 13 civilians have been killed.