A factory processing US hazardous waste in Mexico has promised to relocate what authorities call its “most polluting” operations following a Guardian investigation.

The plant in the Monterrey metropolitan area recycles toxic steel dust sent by the US steel industry and recovers zinc, according to that reporting, which was produced in partnership with Quinto Elemento Lab, a Mexico investigative journalism unit. It revealed evidence of heavy-metals pollution in the surrounding neighborhoods.

The factory, Zinc Nacional, has since been contending with inspections and threats of closures by environmental regulators, court actions and media scrutiny.

Neighbors have held repeated demonstrations outside the plant, carrying signs with slogans such as “Take your mess to the US” and “Your millions are not worth our lives.”