Mexican authorities said Tuesday they staged 153 raids over the last year on a train known as "La Bestia" that rolled toward the U.S. border crowded with hundreds of Central American migrants.

Following a big surge in child migrants reaching the U.S. border last year, Mexico's government cracked down on routes commonly used by migrants to travel from Guatemala to the U.S. border.

The head of the National Immigration Institute, Ardelio Vargas, said the 153 train raids were part of 758 immigration inspections over the last year.

Raids were also carried out on bars, restaurants and hotels where migrants were either held or forced to work, and immigration agents also targeted buses, trucks and other means of smuggling migrants.

Authorities began setting up highway checkpoints and raiding trains in mid-2014 to discourage clandestine migration from Central American countries like Guatemala, Honduras and El Salvador.

But it was the train — a decrepit freight line where boxcar roofs were once completely covered with migrants — that drew Mexico's greatest attention. While some suspected the first raids on the train in August were merely for show, Vargas said Mexico intends to keep migrants off the boxcars.

"The consequences of a railroad accident with 700 or 1,200 migrants on board would have been very regrettable," Vargas said. "We can't be so irresponsible as to allow migrants to continue risking their lives on a freight line that has all the deficiencies it has."

There are some indications that migrants may have switched to taking buses, a somewhat more expensive route through Mexico.

On Tuesday, the institute reported that 101 Central Americans were caught aboard two buses in the north-central state of Zacatecas.

Vargas also said Mexican immigration agents assisted 23,078 child migrants of various nationalities between January 2014 and February 2015. It was not clear how many of those minors were repatriated to their home countries.

Vargas said 37 percent of the minors — or about 8,540 — were unaccompanied.