Prior to its electrification, the line was initially operated by steam locomotives; during this period, the Ricken Tunnel acquired a negative reputation because of its relatively steep gradient and the lack of adequate ventilation, which caused smoke to accumulate and linger within it.

No substantial alterations were made to the tunnel to address its apparent ventilation issues prior to a fatal incident occurring.

On 4 October 1926, a steam hauled freight train stalled while inside of the tunnel whilst attempting to ascend the gradient; this unplanned stop was a result of the use of the poor quality briquettes that were being used as fuel for the locomotive.

Despite multiple attempts to rescue the train crew, a total of nine railway employees died of carbon monoxide poisoning, which included three of the rescuers.

These have been partially attributed to the surrounding geology, which consists of a high proportion of clay minerals and anhydrite rocks, that absorbs water and swells, with the dimensional changes causing damage to the tunnel walls.