The depth of Japanese companies’ involvement in Mexico’s auto industry is visible at Ashimori Industry’s factory on a vast industrial park in Guanajuato state, 400km north-west of Mexico City.

A group of mostly female workers clad in baseball caps and gloves lean over workstations at the plant, in the heartland of Mexico’s auto industry. They are assembling tiny plastic and metal parts for seatbelt safety mechanisms.

Ashimori, a Japanese car-parts manufacturer, set up the factory in 2012, shortly before Mazda began production at a nearby vehicle assembly plant. The facilities are part of the Japanese auto industry’s $18bn of investment in Mexico, both in vehicle final assembly and component manufacturing. The decisions were made based on low labour costs and unfettered access to the US market. The Ashimori workers also make airbags, sun shades and other components for Honda, Mazda and other big manufacturers.