OKLAHOMA CITY (AP) — An investigation into a virtual charter school that has grown to become the largest public school in Oklahoma has been delayed due to inadequate transparency with public funds and a lack of cooperation by some employees, the state's multicounty grand jury said in a report issued Thursday.

The grand jury said it issued the interim report into Epic Charter Schools, even though the investigation is ongoing, because parents and policymakers need to know about their concerns.

“The investigation continues into whether public funds may have been used inappropriately," the report states. “Due to the lack of transparency in accounting for the funds, international avoidance of disclosure of information by a private entity, and lack of cooperation; the investigation is unable to be completed at this time."

Fueled by skyrocketing enrollment amid the coronavirus pandemic that forced closures of traditional districts, Epic Charter Schools has grown to become the largest district in the state, with more than 60,000 students. From 2015 to 2020, the school received more than $458 million in state and federal funds.

Among the biggest concerns of state investigators and the multicounty grand jury is the school's longtime management company, Epic Youth Services, a private, for-profit company that has received a 10% management fee paid for by public funds. The fee has generated more than $45.9 million for the school's founders, David Chaney and Ben Harris, since 2015, according to the report.

An Epic spokeswoman, Shelly Hickman, said in a statement that since October, Epic's governing board has made a number of corrective actions including Epic Youth Services “no longer operationally or financially managing or controlling the school."

“The school itself has fully cooperated in providing public records," Hickman said. “We will continue to fully cooperate in sharing any information we have with the grand jury."

State investigators alleged in 2019 that the Chaney and Harris embezzled millions of dollars in state funds through an illegal scheme to artificially inflate enrollment numbers. But the two men have denied wrongdoing, and no charges have ever been filed.

Since then, State Auditor and Inspector Cindy Byrd released a scathing audit of the school's activities and finances, and the attorney general announced the appointment of a special attorney to head up an investigation into its operations.