At least two members of the Hamas terror group were killed and several injured in a tunnel collapse in the Gaza Strip on Sunday evening.

Conflicting reports in Palestinian media outlets say between two and five people were killed when the tunnel collapsed beneath the city of Rafah in the southern end of the coastal territory, along the border with Egypt.

At least two were said to have been injured and one person may still be missing.

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One report said unseasonable rains had caused the collapse, while another outlet reported that the Egyptian army had detonated the end of the tunnel that entered its territory, and flooded the remainder.

The collapsed tunnel was the 12th reported incident of its kind since the beginning of the year.

At least 16 people, most of them reportedly members of the Izz ad-Din al-Qassam Brigades, Hamas’s armed wing, have been killed in the collapses.

It is not clear what is causing the collapse of many of the tunnels, which serve a variety of purposes, from smuggling goods and firearms from the Sinai Peninsula to carrying out terror attacks against Israeli towns near the Gaza border.

Israeli officials have warned that Hamas has begun rebuilding its network of subterranean tunnels, some of which could extend into Israeli territory and be used for surprise attacks, as they were in 2014.

Jerusalem says it is working on a secret technological solution to the problem. When asked last month if Israeli forces were causing the tunnel collapses earlier this year, IDF Maj. Gen. Yoav Mordechai would only say, “God knows.”

Egypt has also been working to thwart the construction of smuggling tunnels into the Sinai peninsula by flooding them.

Israeli officials have linked many of the recent tunnel collapses to Hamas’s shortage of materials such as wood and cement, needed to strengthen walls of sand.

Hamas has apparently been using fiberglass instead — despite Israel’s prohibition of its entry into the enclave — a material that has proven to be too weak to support the weight of the sand, Israeli sources told the Ynet news site last month.

An Israeli blockade designed to keep weapons and other military infrastructure from entering the Strip severely restricts the movement of people and goods into and out of the territory, and Egypt’s sole border with Gaza has also remained largely closed since 2013 over Egyptian claims that Hamas has supported the Muslim Brotherhood and an Islamist insurgency in the Sinai.