From my source:

The problem of lost and stolen aid is common in Taiz and other areas controlled by Yemen’s internationally recognized government, which is supported by the Saudi-led military coalition. It is even more widespread in territories controlled by the Houthi rebels, the struggling government’s main enemy during the nearly four years of warfare that has spawned the world’s worst humanitarian crisis.

After the release of the AP’s investigation on Monday, the United Nations’ World Food Program for the first time directly accused the Houthi rebels of diverting aid. WFP director David Beasley said in a letter to the Houthis’ leader that if the rebels did not investigate and put an end to theft, the organization would suspend some assistance, potentially effecting nearly 3 million people.