The theft of a metal bar used to link two rails caused the train crash last weekend in the southeastern Mexican state of Tabasco that left 12 dead, the Communications and Transportation Secretariat said.

The secretariat said in a statement Friday that specialized technicians with Ferrocarril del Istmo de Tehuantepec, the operator of the railway line, made that determination.

Between July 2011 and June 2013, that company reported 11 instances of theft of railway parts in the municipality of Huimanguillo, where the derailment occurred last weekend, the secretariat said.

It added that a thorough review of railway infrastructure would be carried out to ensure the future safety of the line.

Seven of the fatalities have been identified as undocumented Honduran migrants who hopped aboard the northbound freight train known as "La Bestia" (The Beast).

Central American migrants headed for the United States ride on top of the freight train or in open-air wagons, with hundreds of people sometimes clinging to the train's cars.

The train derailed around 3:00 a.m. Sunday outside Huimanguillo, a town near Tabasco's border with Veracruz state.

More victims may be found as workers continue the slow, arduous task of removing the tons of scrap metal the train was hauling at the time of the wreck, state authorities said.

Besides the dangers inherent in hopping onto moving trains, Central American migrants must contend with criminals and corrupt Mexican officials.

Gangs kidnap, exploit and murder migrants, who are often targeted in extortion schemes, Mexican officials say. EFE