Update 2:30 pm:

Officials determined the an accidental gas leak from an underground pipe on the property sparked Saturday night's explosion at the Tree Tops Resort in Gatlinburg.

The State Marshall's Office closed the investigation on Sunday at about 5 p.m. Authorities have turned the property back over to the company.

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(WBIR - Gatlinburg) Investigators have determined Saturday night's explosion at Tree Tops Resort was "accidental", according to Gatlinburg Fire Chief Greg Miller. Officials are still trying to figure out exactly what caused the gas leak.

Tree Tops Resort's developer and manager, Charlie Anderson, said, "We believe it was a gas boiler."

Anderson said the resort performs maintenance checks periodically to prevent such incidents.

Three people were taken to the hospital after Saturday night's explosion, one was airlifted to UT Medical Center in Knoxville and the other two were taken to LeConte Medical Center in Sevierville by ambulance. Sunday, the victim's names and current conditions were not available. Fire officials said all three adult victims, one woman and two men, suffered from burns.

The building where the explosion happened is now blocked off. Gatlinburg Fire Chief Greg Miller explained, "The primary explosion was confined to one condo unit, but the concussion of the explosion done some collateral damage to a couple of other units and the parking garage below."

Thirty-five people had to be relocated to other rooms on the resort.

State investigators said it may take a couple of weeks to complete their investigation.

Anderson said the building will be repaired.

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