Ferromex's purchase of 19 units will bring its total fleet of SD70ACes to 116, while the acquisition of 15 units by Ferrosur represents the company's first order for EMD locomotives.
The locomotives will be delivered by June 2015 and will be maintained by the supplier for 11 years.
Both Ferromex and Ferrosur are part of Grupo México, which is part-owned by Union Pacific.
