SIOUX FALLS, S.D. — The internal watchdog of the Health and Human Services Department says the often substandard quality of care at hospitals serving Native Americans is the result of outdated equipment and technology, lack of resources, and difficulty attracting and keeping skilled staff.

The Office of Inspector General on Friday released two reports that looked into the longstanding challenges of the 28 hospitals directly operated by the federal Indian Health Service. The office, which acknowledged that reports of inadequate health care services for Native Americans had been of concern to the federal government for almost a century, criticized the agency’s limited oversight regarding compliance with federal regulations and quality of care, detailing how the agency’s regional administrators had few sources of information to assess the services provided at the hospitals.

The Indian Health Service, commonly referred to as I.H.S., is responsible for providing health care services to enrolled tribal members as part of the government’s treaty obligations to Native American tribes. But the agency has faced challenges for decades, and within the past year has been under increased scrutiny from Congress after inspections of hospitals in the Great Plains uncovered severe deficiencies.

The inspector general’s office said that the Indian Health Service’s eight regional offices conducted activities to monitor the quality of the hospitals, but that those efforts were minimal in some areas.