Iranian trucks carrying suspicious chemicals were stopped by Turkey on their way to Syria, Turkish Foreign Minister Ahmet Davutoglu said on Sunday morning.

According to Davutoglu, Iran claimed the trucks were carrying ingredients to make fertilizer for Syrian farmers, but the same components can be used to create various types of chemical weapons.

This isn’t the first time Iranian trucks transporting apparent military aid to Syria were apprehended by Turkish officials. In January there were a few interceptions made by Turkish security forces. In one incident, four trucks carrying weapons were stopped, and in another missiles and components for making chemical weapons were caught at the border.