Hamas is overcoming Israel’s restrictions on cement and other materials intended for the rehabilitation of Gaza — but co-opted for the construction of terror tunnels – by using fiberglass to fortify the underground structures, the Hebrew news site Walla reported on Tuesday.

According to the report, this development has caused the Israeli defense establishment to consider banning the entry into Gaza of the dual-purpose materials used for the production of fiberglass.

Over the last few months, Coordinator of Government Activities in the Territories Yoav Mordechai and UN officials have increased supervision over the entry of building materials into Gaza through the mechanism for the rehabilitation of the Strip following Operation Protective Edge, Israel’s war against Hamas in the summer of 2014.

In the course of this enhanced monitoring, UN supervisors revealed three weeks ago that building materials earmarked for the renovation of private homes in Gaza were transferred to Hamas operatives. In response, Israeli Defense Minister Moshe Ya’alon – at Mordechai’s recommendation – gave the directive for an immediate halt to the transfer of cement into Gaza until further investigation. This will be carried out, according to Walla, by way of a computerized system that tracks the movement of building materials, and by observing surveillance footage from cameras installed at various warehouses.

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Following an investigation conducted by UN monitors, two people were fired – the main supplier of building materials to the Palestinians in Gaza, and the Hamas official responsible for distributing the materials. In addition, it was decided to blacklist those Palestinian families who sold their vouchers for building materials to Hamas.

Meanwhile, in the wake of last week’s revelation that a new terror tunnel from Gaza into Israel had been unearthed, another development was cleared for publication on Tuesday: that customs officials and Shin Bet (Israeli security agency) officers at the Nitzana border crossing — used by Egypt, Israel and the Palestinian Authority — thwarted the smuggling of four tons of ammonium chloride concealed in a salt shipment before Passover. This chemical, security sources said, can be used to manufacture hundreds of long-range rockets. According to the Shin Bet, the importer, a resident of Gaza, is associated with Hamas operatives, Walla reported.

This revelation comes a day after Ya’alon announced the reopening – at an unspecified date – of the Erez border crossing between Israel and northern Gaza, to ease congestion at the Kerem Shalom crossing in the southern part, where all goods have been transferred into the Strip from Israel. Erez was closed in 2008, as part of the blockade of Gaza, following Israel’s withdrawal from the territory in the summer of 2005, a few months before Hamas took control over the Strip.

The revelation also coincided with a surprise visit to the Gaza area on Tuesday by Ya’alon, Prime Minister Benjamin Netanyahu and IDF Chief of General Staff Gadi Eizenkot to tour the site of the terror tunnel shaft that was uncovered two weeks ago.

Mere hours after the visit, as Walla reported, IDF troops near the Gaza border fence were fired on from the Hamas-controlled enclave, though no one was injured in the attack.