An audit by the Homeland Security Inspector General says immigration authorities were inconsistent with I-9-enforcement against employers. The result is based on a review of cases from the late Obama years and early Trump presidency.

Immigration and Customs Enforcement checks if companies hire undocumented people by inspecting I-9 records, which say what proof workers gave to show they’re legal.

But the Homeland Security Inspector General says agents did not properly document why I-9 fines against some companies were cut by as much as 58%.

The report also says ICE gave more than one in five employers a letter saying they’d passed inspection. But the companies actually had I-9 violations not covered by the agency’s outdated enforcement guide.

The independent auditor also says ICE did not follow up on most I-9 warnings given to employers in the cases sampled.