The U.S. Army has lost track of more than $1 billion worth of weapons and other equipment destined for local allies combating the Islamic State (ISIS/ISIL) in Iraq, including an Iran-allied group of Shiite fighters, reveals a report.

According to a declassified government audit of the Iraqi Train and Equip Fund obtained by Amnesty International through a Freedom of Information Act (FOIA) request, hundreds of Humvees and mortars, as well as tens of thousands of rifles, remain unaccounted for due to a lack of central database for keeping track of U.S. taxpayer-funded military equipment.

“This audit provides a worrying insight into the US Army’s flawed – and potentially dangerous – system for controlling millions of dollars’ worth of arms transfers to a hugely volatile region,” declared Patrick Wilcken, the arms control and human rights researcher for Amnesty, in a statement.

“It makes for especially sobering reading given the long history of leakage of US arms to multiple armed groups committing atrocities in Iraq, including the armed group calling itself the Islamic State,” he continued.“The need for post-delivery checks is vital. Any fragilities along the transfer chain greatly increase the risks of weapons going astray in a region where armed groups have wrought havoc and caused immense human suffering.”

The U.S. Army provided the unaccounted weapons and other military equipment to the U.S.-backed Iraqi Army, Kurdish Peshmerga troops, and the Iran-allied Popular Mobilization Units (PMU), a predominantly group of Shiite fighters sanctioned by Baghdad.

Amnesty International has accused PMU fighters, also known as the Popular Mobilization Forces (PMF) and al-Hashd al-Shabi, of committing atrocities against civilians in Iraq using weapons from the United States and other countries.

The report, which covered September of last year, noted that the Pentagon fails to track the weapons after being transferred to the Baghdad-based government.

U.S. Department of Defense officials “did not have accurate, up-to-date records on the quantity and location” of a vast amount of equipment pouring into Iraq and Kuwait to provision the Iraqi Army, reveals Amnesty International in a press release.

“The equipment – which include[s] hundreds of Humvee armored vehicles, tens of thousands of assault rifles and hundreds of mortar rounds – was destined for use by the central Iraqi Army, including the predominantly [Shiite] Popular Mobilization Units, as well as the Kurdish Peshmerga forces,” it adds.

In the report, auditors reveal several lapses in the manner in which U.S. taxpayer-funded military equipment is logged and monitored beginning from the point of delivery.

Among the shortcomings, are:

Fragmentary record-keeping in arms depots in Kuwait and Iraq, with information logged across multiple spreadsheets, databases and even on hand-written receipts.

Large quantities of equipment manually entered into multiple spreadsheets, increasing the risk of human error.

Incomplete records meaning those responsible for the equipment were unable to ascertain its location or status.

In fiscal year 2015 alone, which includes the time covered by the government audit, the U.S. Congress allocated $1.6 billion for the fight against ISIS.

Amnesty International reports:

Meanwhile, a previous Department of Defense audit in 2015 pointed to the fact that the Iraqi armed forces applied even laxer stockpile monitoring procedures. In some cases, the Iraqi Army was unaware of what was stored in its own warehouses, while other military equipment – unopened and uninventoried – was stored out in the open in shipping containers.

“Sending millions of dollars’ worth of arms into a black hole and hoping for the best is not a viable counter-terrorism strategy; it is just reckless,” said Wilcken.

Amnesty acknowledges that the U.S. military has vowed to improve its systems for tracking and monitoring future military equipment transfers to Iraq.

“However, the Department of Defense made almost identical commitments in response to a report for Congress as long ago as 2007 that raised similar concerns,” it points out.