By CBS 2 Chicago Staff

(CBS) — The cause of the massive fire at the Chemtool plant in Rockton earlier this month was accidental, likely caused when a scissor lift struck a valve.

On June 14, a worker for an outside contractor was replacing insulation on an elevated heat transfer piping network that was part of the site’s system for heating certain vessels used in the manufacturing of lubricating greases. This network of piping carried heated mineral oil.

READ MORE: Chicago Police Restrict Time Off For Officers Amid Battle Between City Hall, FOP Over COVID-19 Vaccine Mandate

Rockton Chief Kirk Wilson said that the scissor lift used to reach the area struck a valve or pipe, causing mineral oil to leak.

READ MORE: Artist Nate Baranowski Uses Chalk Art To Bring Halloween Festivity To Howard Street In Rogers Park

Chemtool operators promptly detected the release and shut down the boiler. They were in the process of placing containment booms, as well as de-pressuring the heat transfer piping network, when the fire ignited.

MORE NEWS: City Officials, Community Leaders Hit Streets To Urge People To Get First COVID-19 Shots, Boosters, And Flu Shots

The investigation has not yet determined the source of ignition.

CBS 2 Chicago Staff