Mexico is calling for a full investigation after U.S. border guards fired tear gas into crowds of migrants and protesters on Mexican soil.
In the ensuing panic, a Reuters photographer captured one mother rushing her twin, five-year-old daughters to safety.
(SOUNDBITE) (Spanish) MARIA MEZA, A MIGRANT MOTHER, SAYING: "Well I felt sad, scared and wanting to cry.
That's when I grabbed my daughters and started running.
At that moment I thought I was going to die with them because of the gas.
We ran and we fell into the mud (ditch) and struggled to get up amidst the gas.
A young man gave me his hand and pulled me up to my feet." Thirty-five-year-old Maria Meza said she fled north from Honduras with five children and on Sunday tried to claim asylum at the U.S. port of entry, but she and other migrants were blocked by Mexican police.
Some migrants pushed through and tried to reach the U.S., when they were hit with tear gas.
(SOUNDBITE) (Spanish) MARIA MEZA, A MIGRANT MOTHER, SAYING: "I wasn't expecting it.
We never thought they were going to fire these bombs where there were children, because there were lots of children, not just mine.
There were more children with mothers there.
They also started running too just like me." On Monday Mexico's foreign ministry presented a diplomatic note to the U.S. government calling for "a full investigation" into what it described as non-lethal weapons directed toward Mexican territory.
U.S. President Donald Trump was asked Monday about the use of tear gas on children.
(SOUNDBITE) (ENGLISH) U.S. PRESIDENT DONALD TRUMP SAYING: "They're not, as you know, they're not.
They had to use because they were being rushed by some very tough people and they used tear gas.
Here's the bottom line: no one's comig into our country unless they come in legally." Trump sent military forces to the southern border to deter migrants from entering, and had demanded Mexico send them back home to Honduras, Nicaragua, and El Salvador.
Several thousand migrants, mostly Hondurans, have been waiting in Tijuana for more than week, unsure of their fate.
(SOUNDBITE) (Spanish) HONDURAN MIGRANT, JOSUE CACEREZ, SAYING: "Some people are saying that they are going to take us to another shelter because there is no room for us here, because they have hit their capacity.
And many people are telling us that we are not going to have any other option but accept asylum here in Mexico." Mexico has been in negotiations with the United States over a possible scheme to keep migrants in Mexico while their asylum claims are processed.