The Israel Defense Forces have released footage of a tunnel in the city of Khan Younis in southern Gaza where it said Hamas held around 20 hostages at different times, CNN reports.

The tunnel was located in the center of Khan Younis and ran about 830 meters (0.51 miles) at a depth of 20 meters (66 feet), the IDF said.

There were booby traps, explosives and various obstacles inside the tunnel, according to the IDF, which said it encountered and killed several Hamas operatives as it entered the tunnel.

The IDF found no hostages in the tunnel but said, based on testimonies from former hostages and DNA evidence, that about 20 hostages were held in there at different times, some of who have been released while others remain held in Gaza.