Authorities ordered the closure of two furnaces at a recycling plant in Mexico that processes hazardous waste exported from the United States after investigations by The Guardian and Quinto Elemento Laboratories revealed heavy metal contamination in nearby homes and schools.

On Thursday, a team from the environmental agency of the Mexican state of Nuevo León visited the plant in a densely populated area of ​​the Monterrey metropolitan area.

The actions follow a report published on Tuesday that traced how U.S. Steel shipped contaminated dust left behind from recycling scrap metal to a national zinc plant where it was processed in furnaces.

The reporting team worked with Martín Soto Jiménez, a toxicology researcher at the National Autonomous University of Mexico (Unam), to collect soil and dust samples from homes and schools surrounding the factory.

Samples showed high levels of lead, cadmium and arsenic, including lead dust on a window sill at one elementary school that was 1,760 times the U.S. action level.

Emissions reports Zinc Nacional files with the federal government show the company also releases these same heavy metals into the air.

During Thursday's visit, officials found evidence of "emission control system deficiencies" in the soil as well as dust generated by the plant, the agency said in a news release. "Therefore, as a precautionary measure, a furnace suspension was ordered... This measure will remain in force until the Federal Environmental Protection Agency (Profepa) has jurisdiction over the case."

Profepa's environmental regulators arrived at the plant on Friday. An agency public information officer said the federal government has ultimate authority over such facilities that handle hazardous waste.

Zinc Nacional did not respond to questions from the Guardian and the nonprofit reporting group Quinto Elemento Lab about the Monterey shutdown and other reactions to the study's findings. "Oversight by state and federal authorities, as well as various independent audits by customers, suppliers and international certification bodies, have proven that Zinc Nacional complies with applicable regulations and implements international standards," the company said in a press release shared with reporters. It operated.”

It described the furnace closure as "precautionary" and said: "If areas for improvement are identified in our operations, we will make the necessary adjustments to enhance safe working conditions for employees, collaborators and neighboring communities.

The investigation by The Guardian and Quinto Elemento Laboratories has received prominent coverage in local and national media, with a front-page story in the main regional newspaper El Norte over the past four days.

Principals of area daycare schools - including one where high arsenic levels were found in Soto Jimenez - have called on the government to conduct a health investigation.

Residents of San Nicolas de los Garza, a city in the Monterrey region where the plant is located, are organizing a signature collection campaign to complain about the pollution.

“Our goal is just to stop the pollution because the lungs and health of the residents of San Nicolás and the surrounding area are not for sale,” said Roberto Chavarría, a neighbor who lives near the factory and is helping organize explain. He said a peaceful protest was planned for Friday, January 24.

"We are not a dumping ground for America or anyone else."

Susana de la Torre Zavala, a mother of two, attended a school near the National Zinc plant. She said the company is inviting parents to tour the facility and hold a meeting on Thursday. But she said the company has provided few specifics.

"No one showed us any data; they just told us, 'That's not true, everything is fine,'" Torre Zavala said. "We need certainty, transparency - we need additional research."