Israeli forces on Friday probed further into civilian infrastructure in northern Gaza for signs of a Hamas presence, announcing that they had found weapons at a school and guiding international reporters to a tunnel shaft on the grounds of the territory’s largest hospital.

As troops searched the hospital, Al-Shifa, for a third day, Israel announced that it would allow limited shipments of fuel to the enclave to avoid “epidemics” amid the wreckage of the territory.

Israel has been under intense international scrutiny to justify its incursions into Gazan hospitals, which are sheltering thousands of civilians in addition to the sick and wounded. On Thursday night, the Israeli military escorted journalists from The New York Times through a landscape of wartime destruction to a stone-and-concrete shaft on the grounds of Al-Shifa with a staircase descending into the earth — evidence, it said, of a Hamas military facility under the hospital.

But Col. Elad Tsury, commander of Israel’s Seventh Brigade, said military forces, fearing booby traps, had not ventured down the shaft at the hospital. He said it had been discovered under a pile of sand on the northern perimeter of the complex.