An unnamed State Department official said that Secretary of State Marco Rubio spoke to Lebanese President Joseph Aoun Thursday regarding the seizure of hundreds of kilograms of explosives believed to belong to Hezbollah. According to the official, Rubio urged the president not to return the confiscated explosives to the Iran-backed terror group.

“He urged President Aoun to hold accountable all those who ordered, financed, and directed the shipment, and underscored that returning explosives to Hezbollah should be out of the question,” the official said.

Lebanese Prime Minister Nawaf Salam announced Monday that Lebanese forces confiscated the materials from a truck that was traveling to Beirut. He said that the truck held “hundreds of kilograms of explosives.” While not identifying Hezbollah, he vowed that the government would pursue “truth and accountability” in its investigation.

Salam noted that C-4 had been used in “several of the infamous political assassinations in modern Lebanese history.”

According to Reuters, a Hezbollah terrorist claimed ownership of the materials on Hezbollah’s behalf and said that the group had intended to use the explosives against Israel.

According to the U.S. official, Rubio also urged Aoun to allow the Lebanese and Israeli militaries to communicate, despite a 1995 Lebanese boycott law barring Lebanese citizens from speaking to Israelis.

The official quoted Rubio as saying that the law “is routinely used for politicized prosecutions that deter steps towards peace,” adding that the secretary of state “emphasized that the law is impractical and urged direct military-to-military communication between Lebanese and Israeli forces for deconfliction, which would help to reduce miscalculation and to advance sequenced implementation of the Trilateral Framework.”