Boxes of aid destined for Gaza sat stranded atop a truck and flatbed trailer Sunday, just meters from Egypt’s Rafah border, as frustrated drivers and U.N. officials criticized delays in delivering critical food and medicine to the enclave.

Seven aid officials and three truckers described a range of obstacles, including shipments rejected over minor packaging and paperwork issues, heightened scrutiny of potential dual-use for military purposes, and limited working hours at the Israeli border crossing.

The stalled supplies bore blue World Health Organization logos and labels identifying items such as topical medications and suction devices for wound care.

A WHO employee at the crossing said the cargo was blocked for containing “illegal medicines.”

Reuters visited Egypt’s border with Gaza Monday on a trip organized by the Elders, a group of former world leaders founded by the late South African President Nelson Mandela that supports a two-state solution to the Israeli-Palestinian conflict.