The Transportation Safety Board of Canada is set to release a report on Wednesday about a train derailment due to a bridge failure in the aftermath of the Calgary flooding in 2013.

On June 27, 2013, the supports of the Bonnybrook Bridge, which spans the Bow River in southeast Calgary, gave way under the water as flood waters had scoured the river’s bottom days earlier.

A Canadian Pacific freight train was crossing the bridge when the collapse occurred and six tank cars, filled with petroleum dilutant, teetering on the brink of falling into the water, which had the potential to create a massive ecological disaster.

Crews spent several days unloading the material and removing the cars from the damaged bridge.

The TSB report is expected to include details about CP’s protocol for inspecting bridges, tracks, rail cars, and locomotives after floods.

The agency is also expected to reveal what exactly happened and why to prevent future incidents like this.

(With files from the Canadian Press)