NASHVILLE (AP) - A private inspector and police are blaming "mechanical failure," but government investigators are still sorting out exactly how a Ferris wheel seat flipped over at a Tennessee county fair, sending three girls plummeting 30 to 45 feet to the ground.

The accident left a 6-year-old girl with a traumatic brain injury, and has prompted renewed scrutiny of the lack of state or federal inspections to ensure that traveling carnival ride has been safely installed before it opens for business.

Tennessee authorities decided to stop doing inspections altogether after a 2014 audit found shortcomings in the state's regulatory program for rides at fairs and amusement parks.

The state relies instead on private inspectors hired by ride operators as well as inspections in other states to determine if roller coasters, zip lines and Ferris wheels are safe. But there is no state requirement for an inspection to confirm that traveling equi pment has been properly reassembled before children climb on board.

Greeneville Police Capt. Tim Davis said at a news conference late Tuesday that "mechanical failure" appeared to have caused the basket the girls were riding in to overturn Monday night at the Greene County Fair in eastern Tennessee.

According to media reports, Davis said police had not been able to confirm reports that the basket was rocking before it flipped.

Frank Gunther, an inspector hired by Family Attractions Amusement, also cited mechanical failure at the news conference Tuesday night. Three other inspectors - the police captain didn't say who they represent - are at the scene investigating.

Bracken Burns, the director of trauma services for Johnson City Medical Center, said the 6-year-old was critically injured, while her 10-year-old sister and a 16-year-old female who shared their seat were in stable condition. Burns said the 10-year-old's forearms were injured, and that he co uldn't release information on the other girl.

The company received its permit to operate the Ferris wheel in Tennessee for the next three months based on a June inspection in Indiana, according to state Department of Labor and Workforce Development spokeswoman Jennifer Farrar.

Because of this 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.

The Valdosta, Georgia-based company did not return a message left on the voicemail of the phone number listed on its last inspection report.

In a follow-up to the audit last year, the state Department of Labor and Workforce Development 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 did approve nearly $490,000 for this fiscal year to bolster the state's Amusement D evice Unit with five new employees, but they are not inspectors; they will 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.

Tennessee shifted responsibility for ride inspections from the state Department of Commerce to the Department of Labor and Workforce Development in 2009, but failed to develop a "viable amusement device regulatory unit" thereafter, the 2014 audit found.

Auditors said mistakes in record-keeping and a lack of inspectors created "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."

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. In Gatlinburg, a woman's wrists and knee caps were fractured when she was ejected from a ride. At three different attractions in Pigeon Forge, people suffered a broken arm on a roller coaster and back injuries were reported after doing flips at a trampoline park and getting hit from behind on an alpine coaster.