Mexico now faces unprecedented situation of having three caravans stretched out over 500kms of highways in the southern states of Chiapas and Oaxaca, with a total of about 6,000 migrants.
A third caravan of migrants — this time from El Salvador — waded over the Suchiate River into Mexico on Friday, bringing another 1,000 to 1,500 people who want to reach the US border.
The third caravan tried to cross the bridge between Guatemala and Mexico, but Mexican authorities told those traveling in it they would have to show passports and visas and enter in groups of 50 for processing.
The Salvadorans expressed misgivings that they would be deported, so they turned around and waded across a shallow stretch of the river to enter Mexico.
Although police were present, they did not try to physically stop the migrants, who later walked along a highway toward the nearest large city, Tapachula.
Unprecedented situation for Mexico
Mexico is now faced with the unprecedented situation of having three caravans stretched out over 500 kilometers of highways in the southern states of Chiapas and Oaxaca, with a total of about 6,000 migrants.
The first, largest group of mainly Honduran migrants entered Mexico on October 19 and is now in Donaji, Oaxaca.
Though the first caravan once numbered as many as 7,000, Mexico's Interior Department estimated that, as of Friday, it numbered only 3,000 people.
The second caravan, also of about 1,000 to 1,500 people, entered Mexico earlier this week and is now in Mapastepec, Chiapas. The second group includes Hondurans, Salvadorans and some Guatemalans.
In addition, the government identified a fourth, smaller group of 300 Central American migrants walking further ahead, in the Gulf coast state of Veracruz.
It remained unclear whether the first caravan will make a turn east to Mexico City, or try to reach the nearest and most dangerous stretch of border, which lies almost directly north. Divisions began to appear among caravan participants about what route to take.
Weathering tough conditions
It also remained unclear how many migrants would make it; 20 days of scorching heat, constant walking, chills, rain and illness had taken their toll. Mexico's Interior Department says nearly 3,000 of the migrants in the first caravan have applied for refuge in Mexico; hundreds more have returned home.
Honduran migrant Saul Guzman, 48, spent the night under a tin roof in the Oaxaca state town of Matias Romero with his son Dannys, 12, before setting out for the town of Donaji, 47 kilometers north.
"I have been through a lot," said Guzman.
"I want to spend my time differently, not in poverty."
In his hometown of Ocotepeque, Honduras, he left behind a coffin, either for his mother, who suffers dementia, "or for me, if I don't make it," Guzman said.
The migrants had already made a grueling 65km trek from Juchitan, Oaxaca, on Thursday, after they failed to get the bus transportation they had hoped for. But hitching rides allowed them to get to Donaji early, and some headed to a town even further north, Sayula.
The migrants have not said what route they intend to take, but any trek through the Gulf coast state of Veracruz could take them toward the Texas border.
Another large caravan early this year passed through Veracruz but then veered back toward Mexico City and eventually tried to head to Tijuana in the far northwest. Few made it.
Immigration agents and police have been nibbling at the edges of the first two caravans.
A federal official who was not authorised to be quoted by name said 153 migrants in the second caravan were detained on Wednesday during highway inspections in Chiapas, a short distance from the Guatemalan border.
There was also pressure on the first caravan. Not only did the hoped-for buses not arrive, but federal police began pulling freight trucks over and forcing migrants off, saying their habit of clinging to the tops or sides of the trucks was dangerous.
At other points along the route, police have forced overloaded pickups to drop off migrants. On previous days, they have ordered passenger vans to stop helping with transportation.
President Donald Trump has ordered US troops to the Mexican border in response to the caravans of migrants. More than 7, 000 active duty troops have been told to deploy to Texas, Arizona and California.
Trump says has told the US military mobilising at the southwest border that if US troops face rock-throwing migrants, they should react as though the rocks were "rifles." He also plans to sign an order next week that could lead to the large-scale detention of migrants crossing the southern border and bar anyone caught crossing illegally from claiming asylum.
'We aren't killers'
Though some migrants clashed with Mexican police at a bridge on the Guatemala border, they have repeatedly denied coming with any ill intentions, saying they're fleeing poverty and violence.
"We aren't killers," said Stephany Lopez, a 21-year-old Salvadoran with the first caravan.
Similar caravans have occurred regularly over the years and passed largely unnoticed, but Trump has focused on the latest marchers seeking to make border security a hot-button issue in next week's mid-term elections.