It is unclear why Sinwar or his entourage would have the passport in their possession and Israeli officials have yet to comment.
Benjamin Netanyahu’s government has long accused UNWRA – an aid agency for Palestinian refugees – of being connected to Hamas.
Last month, Fateh Sherif Abu el-Amin, the leader of Hamas in Lebanon, was killed in an Israeli air strike.
El-Amin was later revealed to have been working as an UNRWA teacher and principal in Lebanon until being suspended in March.
It was the latest in a series of scandals relating to the agency.
In August, it fired nine of its staff members after finding that they “may have been” involved in the October 7 massacre.
Farhan Haq, the UN spokesman, said UNRWA had “sufficient information in order to take the actions that we’re taking – which is to say, the termination of these nine individuals.”
That announcement followed a near six-month internal investigation into claims made by Israel that 19 of its staff members took part in the Oct 7 attack.
At least one UNRWA staff member was caught on video kidnapping an Israeli civilian from Kibbutz Be’eri on Oct 7.