The U.S. poured more than $50 million into drug treatment programs in Afghanistan between 2013 to 2018 — but it’s unclear if the programs are making a difference, according to the Special Inspector General for Afghanistan Reconstruction.

Afghanistan is one of the world’s top producers of opioids and approximately 2.9 million to 3.6 million people in Afghanistan are users of drugs like opium and heroin, according to the 2015 Afghanistan National Drug Use Survey conducted by SGI Global LLC.

Meanwhile, the U.S. is battling an opioid epidemic at home. The National Institute on Drug Abuse estimates approximately 1.7 million people faced substance use disorders connected to prescription opioid pain relievers in 2017.

In total, SIGAR said the State Department’s Bureau of International Narcotics and Law Enforcement Affairs dished out at least $50.5 million on 41 drug treatment programs implemented by its partners, the Colombo Plan and the United Nations Office on Drugs and Crime, from January 2013 to April 2018.

Despite these efforts, SIGAR determined INL was not measuring the projects’ performance and impact as State Department and Government Accountability Office guidance suggest.

“SIGAR found that because INL has not evaluated the performance of its projects, INL cannot determine the progress or impact its drug treatment projects have had,” the report says.

The report explained that the Colombo Plan and UNODC were responsible for measuring and providing information on their performances and INL did not independently confirm the information. Additionally, INL’s Agreement Officer’s Representatives didn’t visit project locations.

Due to the lack of oversight, SIGAR determined that INL “lacks an understanding” regarding the impact of its project in Afghanistan and said INL was incapable of “making informed decisions about its ongoing drug treatment projects.”

SIGAR issued a series of recommendations, such as requiring INL to fully follow State Department and INL performance measurement guidance and set project requirements outlining objectives and specific actions that must be met. INL agreed with all of SIGAR’s recommendations.

The White House said in April that Afghanistan’s heroin production does not have a significant impact on the opioid crisis in the United States, but undermines the U.S.’s counter-terrorism efforts in the country by generating revenue for the Taliban.

Reducing Afghanistan’s drug production and trade has been a major priority for the U.S. dating back to 2002 and, according to the SIGAR report, the U.S. government has shelled out nearly $9 billion since then on counternarcotics efforts.