KNOXVILLE, Tenn. (WATE) — State safety regulators have launched an investigation into a collapsed trench at a Knoxville construction site that left two men injured.

Two construction workers were installing piping at a new apartment complex off of Inskip Drive on Monday when it collapsed, partially covering them in mud and gravel. They were freed after several hours by the Knoxville Fire Department and other city workers.

The Tennessee Occupational Safety and Health Administration announced Tuesday that their investigation will work to determine what circumstances led to the collapse.

A TOSHA spokesperson said a workplace injury investigation can take six to eight weeks to complete and typically involves surveying the scene, reviewing company procedures, and conducting interviews.

The results of the investigation will be available to the public upon completion.