A Yokohama Tire factory in Mississippi says it has fired 29 employees for not meeting job requirements.

The Clarion-Ledger reports that a local news station says employees at the plant were fired for using fake worker certifications and that the workers obtained fraudulent certificates from a job-training program that companies use to determine the aptitude of potential hires.

Yokohama Tire Manufacturing Mississippi (YTMM) says it is “actively investigating the situation and has created new measures to prevent this from occurring in the future.”

“People are our most important asset at YTMM,” said Osamu Zushi, YTMM President. “We’re extremely proud of our local workforce and won’t let this unfortunate situation take anything away from the great work they provide.”

YTMM, which produces commercial truck tires, opened in 2015 and currently has 665 employees.