The attack reportedly affected families including men, women and children who arrived last month with a migrant caravan that originated in the Honduras.
US Customs and Border Protection (CBP) said in a statement that the tear gas was aimed at what it claimed were rock throwers on the Mexican side who were preventing US agents from assisting children being passed over concertina wire, AP reported. CBP also recorded that 25 migrants were detained on Tuesday.
US President Donald Trump has repeatedly threatened to close the US southern border if he does not get the funding he seeks to build a hotly-contested border wall. The president has also claimed that another caravan was being formed in Honduras and threatened to cut off aid to three Central American states for failing to stop such developments.
Mexico City authorities have said that over 8,200 asylum-seeking migrants from Central America have reached Mexico, with around 7,400 of the migrants staying near the cities of Tijuana and Mexicali just south of the state of California.