A federal investigation into how guards at a Tennessee nuclear weapons plant got copies of questions in advance of a written security skills test has called on the Department of Energy to improve its oversight of private contractors, according to an article from Businessweek.

DOE inspector general Gregory H. Friedman said in a Wednesday report that the questions were widely distributed among security officers at the Y-12 plant in Oak Ridge, the article says. The same plant came under scrutiny after it took hours for the guards to respond when three anti-nuclear protesters cut perimeter fences, made their way to the building housing the nation’s bomb-grade uranium and defaced it with spray paint and blood on July 28.

The report says that the “eyes on, hands off” approach to contractor governance by the National Nuclear Security Administration contributed to the security test being compromised in August when a copy was sent to security contractor WSI-OR, Businessweek reports.

In a written response, DOE’s Office of Health, Safety and Security challenged the oversight recommendation, saying the high cost would outweigh the benefit, the article notes.

Read More: Audit Finds Multiple Security Lapses at Y-12 Nuclear Facility

The investigation into the leaked test was launched after a DOE security official inspecting the operations at Y-12 found a copy of it in a WSI-OR patrol car on August 29. The written test was set to be given to guards the next day, the article says. According to the inspector general’s draft report, DOE canceled the exam and rewrote the test.

The report says that the test materials were sent to WSI-OR because the Federal security official at Y-12 said he wasn’t qualified to review the test and offer suggestions for improvements. The security office confirmed that federal officials overseeing the sites often lack detailed knowledge about security needs.

The test document moved from the government to Y-12’s primary contractor, B&W Technical Services Y-12, which forwarded it to a WSI-OR manager. The report found that the test eventually went to shift captains and subordinates, who treated it as a “training aid.” However, the report found that the original, encrypted government email did not specifically instruct the recipient to keep the test secret, Businessweek reports.

WSI-OR was fired October 1 because of the July intrusion. 

Read More: Guards Replaced Following Tennessee Nuclear Security Breach