Government investigators have not yet determined how a Ferris wheel seat flipped over at a Tennessee county fair, sending three children plummeting 30 to 45 feet to the ground. But the accident that left a 6-year-old girl with a traumatic brain injury sharpened the focus Tuesday on how carnival ride operators are regulated.

After a 2014 audit found shortcomings in Tennessee's regulatory program for rides at fairs and amusement parks, state officials decided to get out of the inspection business altogether. Now, the state relies on private inspectors hired by operators and other states' regulators to determine whether roller coasters, zip lines and Ferris wheels are safe.

Authorities said the three youngsters fell from the ride at the Greene County Fair in eastern Tennessee on Monday night.

In a follow-up to the audit last year, the agency said Tennessee law does not require the state to hire its own inspectors. Funding for the Amusement Device Unit was requested for the budget year ending in June but was denied.

Lawmakers this year did approve nearly $490,000 to bolster the state's Amusement Device Unit with five new employees. They are not inspectors but will be assigned to work on permitting and verification of compliance with inspection and insurance requirements. Within two years, those jobs are supposed to be paid for through program fees.

The Ferris wheel at the Greene County Fair was operated by Valdosta, Georgia-based Family Attractions Amusement. It had received its permit to operate in Tennessee based on an inspection made in Indiana in June.

Dr. Bracken Burns, director of trauma services for Johnson City Medical Center, said the critically injured 6-year-old was in a seat with her 10-year-old sister and a 16-year-old female, who were both in stable condition. Burns said the 10-year-old suffered injuries to her forearms. He said he couldn't give out information on injuries the 16-year-old suffered.

Family Attractions Amusement did not immediately return a message left on the voicemail of the phone number listed on its last inspection report.

Frank Gunther, an inspector hired by the company, told media at a news conference Tuesday night that a mechanical failure caused the accident. Three other inspectors are at the scene investigating.

According to the Greeneville Sun, Family Attractions Amusement was fined in 2013 for violating safety laws in North Carolina after a Vortex ride suddenly lurched into motion as riders were disembarking, injuring four riders and a ride operator.

The Greene County incident was the eighth injury incident reported to Tennessee authorities on amusement rides this summer: They included fractured wrists and knee caps for a woman ejected from a ride in Gatlinburg, and in Pigeon Forge, a broken arm on a roller coaster and injured backs from doing back flips at a trampoline park and being hit from behind on an alpine coaster.

Tennessee recognizes other states' inspections for up to three months before requiring a new permit, according to state Department of Labor and Workforce Development spokeswoman Jennifer Farrar.

Because of Monday's accident, the operators will have to have a new third-party inspection conducted before the ride can qualify for a new annual permit in Tennessee, Farrar said.

Responsibility for ride inspections was shifted from the state Department of Commerce to the Department of Labor and Workforce Development in 2009. But the 2014 comptroller's audit found that department had failed over the ensuing years to develop a "viable amusement device regulatory unit."

According to the audit, mistakes in record-keeping and a lack of inspectors gave rise to "serious concerns about whether the unit is able to ensure that all amusement devices in the state are appropriately permitted and inspected both annually and following accidents and fatalities."