Military officials said it opened some 180 meters (600 feet) inside Israeli territory and had two exits in an open area. The exits were roughly one mile from an Israeli communal village, making Israeli civilians potential targets.
The military invited journalists into the tunnel, dug some 18 meters (60 feet) underground and roughly 1.8 meters (nearly six feet) high. Concrete walls and arches lined the tunnel and electrical cords could be seen along its walls. The military also showed empty food wrappers, work gloves and an axe-like digging tool it said it had found inside. One of the cookie wrappers was dated June 2013, indicating that workers had been inside in recent months.
The military said it was the third tunnel found along the Gaza border fence in the past year. It estimated that 500 tons of cement and concrete were used, and the structure took more than a year to build. It said the tunnel was detected during a routine patrol, and that Hamas blew up the Gaza side of the tunnel after figuring out that Israel had detected it.
The military said it waited a week to publicize the discovery because a search for explosives was underway. The army said an elite engineering corps was sent into the tunnel, but would not say whether explosives were found.
Israel and Hamas are bitter enemies. Hamas does not recognize Israel's right to exist, and since it took power, thousands of rockets have been fired into Israel. Israel carried out major military operations in 2009 and last year in Gaza in response to rocket fire. While various militant groups operate in Gaza, Israel says it holds Hamas responsible. The sides largely have observed a cease-fire since last November.
Prime Minister Benjamin Netanyahu praised the tunnel's discovery and said Israel's resolute policy toward Gaza has led to the "quietest year in more than a decade" along the volatile border.
Maj. Guy Inbar, a military spokesman, said the halt on all construction material to Gaza, announced Sunday, was enacted due to security considerations. For years, Israel prevented the transfer of construction materials into Gaza, saying they could be put to military use.
But since 2010, it has begun to allow some materials in for internationally funded construction projects. This year, it also began allowing in limited supplies of building materials for private use.
Gisha, an Israeli advocacy group that assists Gazan civilians, questioned the Israeli move, saying it appeared to be a punitive act. It urged Israel to allow goods in for internationally supervised development projects.
Apart from Israel, the Gaza Strip also borders Egypt. The Palestinians have dug a network of tunnels under the Gaza-Egypt section of the border to smuggle in supplies like fuel, building materials and food. Hamas has also used the tunnels to smuggle in weaponry.
For years, the tunnels with Egypt have been a lifeline for Gaza, home to some 1.7 million Palestinians. After Hamas took over the territory in 2007, Israel and Egypt imposed a blockade on Gaza. Israel has eased the blockade in recent years, but still restricts the imports of some goods.
Since the summer, Egypt's military has tried to destroy or seal off most of the tunnels after it accused Hamas of fomenting unrest in Egypt. The move followed the popularly-backed coup that ousted Egypt's President Mohammed Morsi, from the Islamist Muslim Brotherhood group, a parent organization of Hamas.
On Sunday, a large blast could be seen in Egypt from the Gaza border town of Rafah. As part of their crackdown, Egyptian authorities often blow up tunnels and buildings used to hide the tunnels that stretch into Gaza.
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Associated Press writer Ibrahim Barzak in Gaza City, Gaza Strip, contributed to this report.
