According to Reuters, Israel coerced and tortured UNRWA workers, subjecting them to "severe physical beatings, waterboarding", to force false confessions about association with Hamas and participation in the Oct 7th attacks.
Israel would later accuse UNRWA of being staffed by Hamas terrorists and participating in attacks against civilian Jews, calling for suspension of funding and blocking UNRWA aid from reaching Gaza civilians.
This resulted in massive starvation of Palestinian civilians and widespread malnutrition among their children.
Most countries which had suspended funding to UNRWA have resumed it, after Israeli claims have not been substantiated, with the notable exception of the US.
Reuters article:
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Independent UN investigators outside the agency carried out the investigation. UNRWA just quotes them in their report.
It is in the same article.