Intensifying conflict in southern Gaza has trapped a team of international doctors, including at least 10 Americans, in a hospital near the city of Rafah, further jeopardizing conditions for both the aid workers and scores of their critically wounded Palestinian patients, medical personnel told The Washington Post.

The medical workers were due to leave Gaza on Monday after a two-week rotation in the European Hospital in Khan Younis, an area near Rafah. Doctors there said they are no longer certain when they can leave or if they can safely reach the border with Egypt. Israel on May 7 seized control of and closed the Rafah crossing, which was relied upon by aid organizations. On Monday morning, a U.N. staff member traveling to the European Hospital was killed when their vehicle — which was marked with a United Nations flag — was attacked.