Six Gaza Palestinians were trapped and one was missing on Thursday after a tunnel caved in, the sixth to collapse since January, a local civil defense official said.

The cave-in was caused by Egyptian flooding of the border zone in its campaign to stop smuggling, the official told AFP.

He described the underground passage from the southern Gaza town of Rafah into neighboring Egypt as a “trade tunnel.”

Israeli officials have said there are dozens of tunnels linking Gaza to the Sinai Peninsula and used to smuggle goods — including weapons — and people in and out of the Gaza Strip.

A local official confirmed that authorities had spoken by cellphone to one of the men trapped by the tunnel collapse and that rescue efforts were under way.

Tunnels falling in have left 12 Gazans dead since the beginning of this year.

Palestinians inspect the damage after Egyptian forces flooded smuggling tunnels dug beneath the Gaza-Egypt border, in Rafah in the southern Gaza Strip, on September 18, 2015. (Photo by Abed Rahim Khatib/ Flash90)

Palestinians inspect the damage after Egyptian forces flooded smuggling tunnels dug beneath the Gaza-Egypt border, in Rafah in the southern Gaza Strip, on September 18, 2015. (Photo by Abed Rahim Khatib/ Flash90)

The news came amid a report that Hamas had begun to dig tunnels that are big enough for weapons-laden trucks to pass through. The Israeli Yedioth Ahronoth daily quoted Egyptian security officials on Thursday as saying that Hamas had started to build “mega-tunnels” more than three kilometers long.

The tunnels, designed to smuggle in arms as well as food and building materials, would compensate for hundreds of smaller tunnels that the Egyptians had either blocked or flooded with seawater, the officials said.

They are designed to bypass the seawater channels used for tunnel flooding and to literally undercut Egyptian efforts to raze all buildings in a roughly one-square-kilometer area aboveground, the report said.

Israeli officials, who said they were unaware of plans to construct such giant tunnels along Gaza’s border with Israel, 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, the report said. Hamas has apparently been using fiberglass instead — despite Israel’s prohibition of its entry into the Strip — a material that has proven to be too weak to support the weight of the sand, Israeli sources told the paper.

Egyptian officials claimed that over the past few months, Hamas has been supplying rockets and deadly homemade weapons such as explosive-filled solar heating drums to Islamic State terrorists in Sinai for their own war against the Egyptian regime.

Used as roadside bombs, the adapted drums, which normally hold water, can destroy a tank, as the Israelis discovered several years ago when such a weapon blew up an Israel Defense Forces tank in the enclave.

Hamas has been accused of training and supplying weapons to jihadis in Sinai.

An Israeli blockade 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.

Hamas security forces next to an Egyptian watch tower on the border between Egypt and Gaza, in Rafah, southern Gaza Strip, September 21, 2015. (Abed Rahim Khatib/Flash90)

Hamas security forces next to an Egyptian watch tower on the border between Egypt and Gaza, in Rafah, southern Gaza Strip, September 21, 2015. (Abed Rahim Khatib/Flash90)

In late 2014, as part of an attempt to restore peace in its restive northern Sinai, Egypt began setting up a buffer zone on its border with Gaza and destroyed hundreds of tunnels. The passages to Egypt are used for transit of commercial goods, cash, people and, allegedly, weapons.

At the other end of the coastal Palestinian territory, near the border with Israel, Gaza’s Hamas rulers have built tunnels to launch attacks, store weapons and at times to stage raids into Israel.

In February, the Egyptian military flooded several smuggling tunnels beneath the Strip’s southern border at Israel’s request, according to Energy Minister Yuval Steinitz.

A senior official in the Egyptian foreign ministry subsequently called the Israeli ambassador in Cairo, Haim Koren, to voice his objection to Steinitz’s remarks, the London-based news site al-Araby al-Jadeed reported.