More than 2,000 migrants, mainly from Central America, have walked out of a city in southern Mexico where they have essentially been trapped.
The migrants walked along a major road leading west and north towards the US border, and pushed past a line of state police who were trying to stop them.
There were minor scuffles, but the migrants continued on their way.
Police, immigration agents and National Guard have broken up smaller attempts at similar breakouts earlier this year.
Tens of thousands of migrants from Honduras, El Salvador and Haiti have been waiting in the southern city of Tapachula for refugee or asylum papers that might allow them to travel, but have grown tired of delays in the process.
Unlike previous marches, the one that started on Saturday from Tapachula did not include as many Haitian migrants, thousands of whom reached the US border around Del Rio, Texas, in September.
In August, National Guard troops in riot gear blocked several hundred Haitians, Cubans and Central Americans who set out walking on a road from Tapachula.
Mexico requires migrants applying for humanitarian visas or asylum to remain in the border state of Chiapas, next to Guatemala, for their cases to be processed.
In January, a larger caravan of migrants tried to leave Honduras but was blocked from crossing Guatemala.
The marches are reminiscent, but nowhere near as large, as the migrant caravans that crossed Mexico in 2018 and 2019.