The IDF announced on Thursday that it had uncovered a second Hamas tunnel extending into Israel, and the Shin Bet security agency revealed on the same day that a Hamas member apprehended last month provided information about the terror tunnel infrastructure.

The newly discovered tunnel was 28 meters deep and within a few kilometers of a tunnel that was uncovered and destroyed one month ago.  As IDf troops struggled this week on the Gaza side of the border fence to uncover the tunnel, Hamas fired at them, including pounding them with mortar barrages. In the last two days, at least 16 mortars were fired at IDF troops.

BREAKING: IDF uncovered 2nd #Hamas terror #tunnel in last 3 weeks through intel, advanced tech, & ground operations pic.twitter.com/YeXOEG9EP5

— IDF (@IDFSpokesperson) May 5, 2016

The attacks on the troops led to Israeli reprisal shelling and a series of airstrikes Wednesday night and Thursday morning, injuring four people in Gaza, according to Palestinian sources. No Israeli injuries were 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 spokesperson confirmed the tunnel began about 100 meters inside Gaza and extended into Israel, however would not say how far it penetrated into Israel. The tunnel was discovered using intelligence information and technological methods.

A two-kilometer long concrete lined tunnel was discovered last month along the Israeli border with Southern Gaza. Officials later said the tunnel may have been dug before the 2014 war and recently reinforced.

Mahmoud Atawnah, a member of Hamas’s armed wing, the Izz ad-Din al-Qassam Brigades, was arrested in April after crossing the border fence into Israel armed with two knives. Under interrogation, he revealed that he has been a member of Hamas for ten years and working on tunnels for the last five.

Atawnah provided information on tunnels routes in the northern Gaza Strip, Hamas’s methods for digging tunnels, use of private homes and institutions as a base for digging, and the materials used in construction.

Atawneh housed a large stash of weapons in his home in Jabalia, in particular Improvised Explosive Devices (IED), weapons, and explosive vests.

The Shin Bet said Atawnah was only one of several Hamas military operatives who are currently under investigation and providing inside information about the tunnels.