The waterpark roof that collapsed late Tuesday night in Ottertail, shuttering the Thumper Pond Resort and leading to the evacuation of 25 to 30 resort guests, was never inspected by state, county or city building code officials, a state official confirmed.

Such inspections are not required in Otter Tail County, one of 65 counties statewide that opted out of inspections. Even in such counties, however, builders are responsible for following the state building code, said Scott McLellan, director of construction codes and licensing at the state Department of Labor and Industry. Forensic engineers combed through roof wreckage on Thursday and Friday, but have not yet stated what caused the roof collapse. No one was injured in the collapse, which occurred at 11:55 p.m. Tuesday.

The 12,000 sq. ft. Northern Hideaway waterpark opened in 2006.

Photo: Thumper Pond Waterpark after April 14, 2015, roof collapse. Photo Credit: Thumper Pond