Gunmen disguised as doctors stormed Sardar Daud Khan hospital in Kabul last Wednesday, with multiple surviving staff telling AFP that insiders including two interns were among the attackers.
The carnage inside the heavily guarded hospital points at a spectacular intelligence failure and spotlights how insurgents have managed to infiltrate top government and military institutions in Afghanistan.
"We have no evidence it was an insider job," Deputy Defense Minister Helaludin Helal, head of a government investigation team, told reporters.
He said 24 hospital and military officials accused of "negligence of duty" are being prosecuted.
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Helal said 50 people were killed by five attackers. But security sources and the survivors, some of whom counted dead bodies, previously told AFP that the death toll exceeded 100.
The Afghan security leadership has come under bitter criticism from lawmakers and social media users over the attack.
MPs are calling for the impeachment of Afghanistan's defense and interior ministers and the intelligence chief, as the country braces for an intense fighting season in the spring.
The savagery of the assault was characterised by how the assailants stabbed bed-ridden patients, threw grenades into crowded wards and shot people from point-blank range.
The Islamic State group claimed it was behind the attack via its propaganda agency Amaq -- hours after the Taliban denied responsibility.
But the survivors AFP spoke to said the attackers chanted "Long live Taliban" in Pashto and attacked all but two wards on the hospital's first floor where Taliban patients were admitted.