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

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.

It is unclear whether the German suspect mentioned in the Spanish statement is the same person that German prosecutors said earlier this week had been arrested on similar charges.

According to AP, 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.

The parts acquired by the network, which has now been dismantled, were identified in drones used by Hezbollah in attacks against Israel after the start of the Gaza war.