The United Nations said it finally gained access to Gaza’s largest hospital, Al-Shifa, following a days-long Israeli raid and found what the head of the World Health Organization called “an empty shell,” with most buildings destroyed.

“The scale of devastation has left the facility completely non-functional, further reducing access to life-saving health care in Gaza. Restoring even minimal functionality in the short term seems implausible and will require substantial efforts to assess and clear the grounds for unexploded ordnance to ensure safety and accessibility for partners to bring in equipment and supplies,” WHO said in a statement.

The WHO said its efforts to reach the hospital “to medically evacuate patients and staff and conduct an assessment were denied, delayed or impeded 6 times between 25 March and 1 April.” According to the WHO at least 20 patients died due to lack of access to care.

The WHO said numerous shallow graves, and many partially buried bodies, were found just outside the emergency department after the Israeli siege.

“During the visit, WHO staff witnessed at least five bodies lying partially covered on the ground, exposed to the heat. The team reported a pungent smell of decomposing bodies engulfing the hospital compound. Safeguarding dignity, even in death, is an indispensable act of humanity,” according to the WHO.

The destruction of Shifa and the main hospital in southern Gaza – Nasser – “has broken the backbone of the already ailing health system,” the WHO said.