Mexico’s Environmental Secretariat Says Ferromex Must Remediate the Damage From Chemical Spill in Sonora

ByCristina Gómez Lima

This article by Cristina Gómez Lima originally appeared in the August 1, 2026 edition of La Jornada, Mexico’s premier left wing daily newspaper.

Naco, Son. — The operator Ferromex, a subsidiary of Grupo México, will have to take on the environmental remediation resulting from the spill that occurred after a train derailment in the border municipality of Naco, the Secretariat of Environment and Natural Resources (Semarnat) reported, specifying that it was more than 70,000 liters of sodium hydrosulfide –that is, 11,000 liters more than previously reported– that ended up in the bed of a Sonora stream.

The agency reported in a statement that federal authorities activated containment protocols and ordered the total temporary closure of the area, while the extent of the contamination that occurred on the night of July 25 on the Cananea-Agua Prieta rail section, in the vicinity of the Cuauhtémoc ejido, in Naco, is precisely determined.

Semarnat specified that the convoy was carrying three gondola cars with approximately 240 tons of copper concentrate and a tank car with 72,000 liters of sodium hydrosulfide (NaHS), of which around 70,300 liters were spilled. It added that the chemical material reached the bed of a stream and the preliminary assessment indicated the impact on an area of around 1.7 square kilometers.

Likewise, the Federal Attorney’s Office for Environmental Protection (Profepa) delimited an area of 5,207 square meters with direct impact, although the definitive extent of the damage has not yet been determined. It detailed that the copper concentrate that the train was also carrying has already been removed in its entirety.

It added that the transfer of 1,700 liters of sodium hydrosulfide that still remained in the damaged tank was also carried out, while the container remains subject to a decontamination process before being removed from the site.

In total, eight duplicate soil samples were obtained at different points, in addition to 18 samples of arthropod fauna at five sites. The laboratory analyses will be decisive in delimiting the affected area and defining the appropriate recovery actions.

Profepa ordered Ferromex to submit a study estimating the magnitude of the contamination along at least 3 kilometers of the affected streambed and to define the remediation program, which will have to be evaluated and approved by the federal environmental authorities.

The Operator Claims It Has Completed the Cleanup

The Grupo México railway company reported that it had completed the containment and cleanup work resulting from the derailment of one of its trains in Naco. Through a statement, it maintained that the work to collect the spilled materials was finished and that rail traffic was restored as of last Wednesday.

The company attributed the accident to a landslide caused by the extraordinary rains recorded in the region: “The mishap occurred in an unpopulated area and was caused by a landslide at the ends of a culvert as a result of the excessive accumulation of water from abundant rains in the region, which weakened the structure of the track,” it stated.

Ferromex asserted that the mishap left no people injured or direct effects on the population, and affirmed that “there is no official record of health consequences related to this event.”