Hamas has released little information regarding the collapses.
The tunnel collapse came just hours after Israeli residents of Gaza border communities woke up to Red Alert sirens from a rocket fired from Gaza. The IDF then retaliated with airstrikes on Gaza.
The IDF explained that it views Hamas as responsible for all projectiles emanating from the Gaza Strip.
Hamas also tested a long-range missile on Sunday, shooting the rocket into the sea.
Meanwhile, Defense Minister Avigdor Lieberman told a Palestinian newspaper in an interview published Monday that, while Israel has no desire to return to Gaza or conquer it, "if they force a new war on us—it will be Hamas's last because we will completely destroy them."