HARRISBURG, PA (CBS) — Auditor General Eugene DePasquale is warning Pennsylvania school districts that they have a responsibility to make sure bus drivers meet state requirements to transport children.

The concern lies with school districts that use contractors to transport students. In one district, the City of Lancaster, DePasquale says as of last June, 16 percent of bus drivers failed to meet at least one state requirement. And he says five were ineligible due to criminal convictions.

“Lancaster is the most extreme. But this not only time that we have found this in school districts. School officials statewide must be extra vigilant,” DePasquale said.

DePasquale says, since 2013, his auditors found five other drivers with criminal convictions; two in Philadelphia – one for aggravated assault and another for arson — and one in Chester Upland for aggravated assault.

Fifty-eight districts in 28 counties were deficient in the process of vetting school bus drivers, something DePasquale says is the responsibility of school districts, not contractors.