CAIRO        -            The United Nations investigators assembled in the departure hall of Sanaa’s airport were preparing to leave with precious evidence: laptops and external drives collected from the staff of the World Health Organization.

These computers, they believed, contained proof of corruption and fraud within the UN agency’s office in Yemen. But before they could board their flight out, armed militiamen from the Houthi rebels ruling northern Yemen marched into the hall and confiscated the computers, according to six former and current aid officials.

The stunned investigators were left unharmed, but flew out without the telltale devices.

The Houthis had been tipped off by a WHO staffer with connections to the rebel movement who feared her theft of aid funding would be uncovered, according to the six former and current officials who spoke on condition of anonymity because the seizure of the computers had not previously been made public.

The October 2018 scene at the Sanaa airport is another episode in the continuing struggle over corruption that has diverted donated food, medicine, fuel and money from desperate Yemenis amid their country’s five-year civil war.

More than a dozen UN aid workers deployed to deal with the wartime humanitarian crisis have been accused of joining with combatants on all sides to enrich themselves from the billions of dollars in donated aid flowing into the country, according to individuals with knowledge of internal UN investigations and confidential documents reviewed by the media.

The media obtained UN investigative documents, and interviewed eight aid workers and former government officials.

The upshot: WHO internal auditors are investigating allegations that unqualified people were placed in high-paying jobs, millions of dollars were deposited in staffers’ personal bank accounts, dozens of suspicious contracts were approved without the proper paperwork, and tons of donated medicine and fuel went missing.

A second probe by another UN agency, UNICEF, focuses on a staffer who allowed a Houthi rebel leader to travel in agency vehicles, shielding him from potential airstrikes by the Saudi-led coalition. The individuals who spoke to AP about the investigations did so on condition of anonymity for fear of reprisals.

Yemeni activists said the actions by the UN agencies are welcome but fall short of the kind of investigation needed to track the millions of dollars in supplies and money from aid programs that have gone missing or been diverted to the coffers of local officials on both sides of the conflict since the start of the civil war.

Over the past three months, the activists have been pushing for aid transparency in an online campaign called “Where Is The Money?” They demand that UN and international agencies provide financial reports on how the hundreds of millions of dollars pouring into Yemen since 2015 have been spent. Last year, the agency said international donors pledged $2 billion for humanitarian efforts in Yemen.

The UN has responded with an online campaign of its own called “Check Our Results,” showing programs implemented in Yemen. The campaign does not provide detailed financial reports on how aid money is spent.

“We see big numbers, billions of dollars reaching Yemen, and we don’t know where they go,” Feda Yahia, a “Where is the Money?” activist, said in a video for the campaign.