Upward of 20 American doctors are trapped in Gaza as a result of Israel’s post-invasion closure of the Rafah border crossing into Egypt, according to sources with knowledge of the plight of two ill-fated medical missions.

Israel has blocked fuel, food, and water from entering Rafah for over a week, leading to severe dehydration among the general population, as well as among the doctors on mission.

Relatives of the doctors were told by the State Department that rescue efforts were underway, including through coordination with the United Nations and the Israel Defense Forces. Yet on Monday, the Israeli military fired on a United Nations vehicle that was traveling to the European Hospital in Khan Younis, near Rafah, killing a U.N. employee and injuring another.

A family member of one of the doctors stranded at the European Hospital said that he suspected the vehicle was part of the rescue mission, but was uncertain. “We are aware that a car that is similarly supposed to be their rescue passage was shot at and UN employees were killed and injured and we fear for their ability to have a safe passage and exit,” said the relative. “We are aware that there is active shelling around the hospital and that staff has been told to stay away from windows.”