The Pentagon’s inspector general said its criminal investigators have opened more than 50 cases related to aid provided to Ukraine, including some involving contractors, but have yet to firm up any allegations.

The investigations, which are at different stages, are looking at issues including “procurement fraud, product substitution, theft, fraud or corruption, and diversion,” the inspector general, Robert Storch, said in a briefing Thursday. “We have not substantiated any such allegations, though that may well change in the future,” he said. Storch also cautioned there would likely be more investigations into abuse or diversions of US equipment “given the quantity and speed” of gear flowing into Ukraine.

The Pentagon is leading Washington’s efforts, along with the State Department and US Agency for International Development, to monitor the roughly $113 billion in aid and funds appropriated for Ukraine, not all of which has been spent, as part of the US-led “Atlantic Resolve” effort to dislodge Russia. A similar process was undertaken for the wars in Iraq and Afghanistan.

Auditors have so far uncovered “stresses and gaps” in providing assistance, he said. For example, audits uncovered incomplete manifests for shipments transfered to Ukraine through Poland.

“As a result, DoD personnel did not have required visibility and accountability of all types of equipment during the transfer process,” they said in a June assessment.

Despite those issues, Storch said the Pentagon so far “has responded well” to Ukraine’s military assistance needs “with the agility to carry out what’s essentially a train and supply mission” before much of the equipment gets to Ukraine.

Storch’s office has over 200 people engaged in Ukraine oversight, and aims to increase the number working inside the country from the current 28, which includes two at the US embassy in Kyiv.

Among other audits still in the works, the Pentagon is evaluating issue around 155-millimeter artillery shells, a key munition for Ukraine, to determine whether the US met its goals while balancing the needs for its own reserves, training and operations.