The Israeli army announced on Monday the discovery of another infiltration tunnel under the Israel-Gaza border.

According to Israel’s Channel 12 news, the tunnel is the 18th one uncovered since the end of the 2014 Gaza war.

“IDF troops just revealed an underground terror tunnel dug from Gaza into Israel,” the army posted on the official English Israel Defense Forces Twitter feed. “How’d we find it? While building an underground security barrier. Why are we building an underground barrier? To stop Gaza terrorists from digging tunnels into Israel. Guess it’s working.”

The age of the tunnel is not yet clear, according to the IDF.

Israel is currently building a 40-mile-long, $700 million anti-tunnel security barrier and detection system along the border with the coastal enclave.

Work on the barrier began in 2016, and is due to be completed by the end of 2019.