Police have arrested four suspects – three in Spain and one in Germany – as part of an investigation into the sale of drone parts to Hezbollah, Spanish police said on Thursday, according to Reuters.

The investigation began in Spain, where officers identified Spanish companies owned by citizens of Lebanese origin who were trading large quantities of components for military drones capable of causing explosions, police said.

Based on an analysis of documents detailing the trade of the above components within Europe, several hundred or even thousands of drones could have been assembled by Hezbollah using the components in question, Spanish police said in a statement.

The light aircraft, which are difficult to detect and stop, are loaded with several kilograms of explosives and are being sent to Israel, police said.

Remnants of drones shot down by Hezbollah found in Israel match the type of components seized by police in Spain and Germany.

Israel and Hezbollah have been exchanging fire since Hezbollah announced a “front of support” for the Palestinians shortly after the October 7 attack by Hamas, triggering Israel’s military offensive in Gaza.

Fighting in Lebanon has killed more than 100 civilians and more than 300 Hezbollah fighters, according to a Reuters count.