Despite four years of trying to fix the problem, the Bureau of Land Management (BLM) inspection program for oil and natural gas wells still has a significant workforce imbalance, according to a report by the Government Accountability Office (GAO).

GAO found that between fiscal 2012 and 2016, BLM distributed most (58%) of the inspection program workload to six of its 33 field offices, but those six offices only had 44% of the program’s workforce. At the same time, the Interior Department agency had 52% of the program’s employees working from 21 offices with a medium level of activity.

Based on its review of documentation and interviews with agency officials, the GAO found BLM took several actions during the four-year period to try to correct the imbalance, including reassigning inspectors to busier field offices. BLM also ordered state offices to conduct internal control reviews of the 33 field offices in July 2012. To date, however, only six reviews have been completed; another five are scheduled through 2020.

According to GAO, officials from BLM state offices said the reviews were hampered by human capital and workload challenges, including long-term vacancies. A senior BLM official also said headquarters didn’t keep track of the reviews and wasn’t aware that so few had been completed.

GAO recommended BLM identify the reasons why the reviews were not completed, and to develop and document procedures to conduct the remaining reviews. It was also recommended that the director take a risk-informed approach to scheduling and conducting the reviews, including the workload facing BLM’s busiest field offices.

The BLM inspection program covers private companies that operate more than 140,000 oil and gas wells on federal and Indian lands. The program also ensures that operators make accurate royalty payments to the federal government.