An investigation has been opened into the cause of a dust explosion Wednesday at the Woodward Wastewater Treatment Plant in Hamilton, ON by the province’s Office of the Fire Marshal and the Technical Standards and Safety Authority, several local news organizations reported.

Dispatched to the facility just after 6 p.m., firefighters arrived on scene and determined that a “minor dust explosion” took place, according to coverage by GlobalNews.ca. Two workers in the plant evacuated safely.

A Hamilton Fire official told The Hamilton Spectator that the blast occurred in a biosolids management system and involved dust created from processing and drying sewage sludge into fertilizer.

Damages are estimated at CAD$75,000, or about $57,440.