A dockworker wearing a mask is seen near containers as he works at port in Ashdod, Israel, March 18, 2020. REUTERS/Amir Cohen

Israel‘s customs authority said on Thursday it found 16 tons of material used for rocket production during an inspection of a shipment from Turkey headed to Gaza, which the ruling Hamas group dismissed as a fabrication.

The customs authority said it had stopped for inspection in July two containers carrying 54 tons of what were supposed to be bags of plaster.

A lab test confirmed some of the bags contained ammonium chloride, the authority added, which it said was used by groups in Gaza “to produce rockets that are eventually launched towards Israel.”

In Gaza, Hamas spokesman Hazem Qassem described the report as “lies.”

“The occupation is forging lies as a pretext to tighten the blockade on Gaza,” Qassem told Reuters.

Israel and Hamas — a widely designated terrorist organization — have fought several wars since 2008, with thousands of rockets fired from Gaza and Israel launching air strikes on the enclave.

With uncertainty growing over who will succeed 87-year-old Palestinian Authority President Mahmoud Abbas, Hamas has stepped up efforts to attract support in the West Bank, a geographically separate territory which Palestinians want as the core of an independent state.

Earlier this month, Israel froze the export of commercial goods from Gaza for several days due to what it said was an attempt to smuggle explosives. Palestinians said the brief ban hit thousands of families.