The Israeli Defense Forces has found a Hamas tunnel extending into Israeli territory for the second time in three weeks, the IDF announced Thursday.

The concrete-fortified tunnel is 90 feet below ground and is only a few kilometers away from the tunnel that was discovered in April, the IDF said. That was the first tunnel found to have extended into Israel since the end of Operation Protective Edge, the war with Hamas that took place in the summer of 2014.

Israeli troops working to uncover the latest tunnel were fired upon on Wednesday by Hamas and Palestinian Islamic Jihad. No Israelis were injured. It was the sixth time in two days that Israeli troops near Gaza were targeted by gunfire or mortar rounds. Israel responded by shelling observation posts and other Hamas targets in Gaza, injuring four, the Times of Israel reported.

“The IDF considers above and below-ground terror activity a violation of the State of Israel’s sovereignty and a threat to its citizens and deems Hamas solely responsible,” a spokesperson said. “It is our job to locate and destroy them.” The spokesman said that the tunnel was found about 100 meters inside Gaza, the first time that Israeli officials have confirmed IDF operations in Gaza since the end of Operation Protective Edge.

The tunnel was discovered using new technology combined with extensive intelligence-gathering, the IDF said.

At least twelve Palestinians have reportedly been killed this year constructing the tunnels, which have been used to ferry attackers into Israeli territory as well as smuggle goods and weapons. Hamas pays over 1,000 operatives to build tunnels and “invests hundreds of thousands of dollars each month in digging activities,” Israel Radio reported last month.

Israel’s continued detection and destruction of the tunnels has forced Hamas to resort to other methods to sneak in weapons and similar material. Israeli border officials discovered four tons of ammonium chloride, which can be used to make rockets and other explosives, hidden in a 40-ton shipment of salt bound for Gaza.

[Photo: IDF / Twitter ]