An AFP journalist reported the crowd size at about 100 and observed the group of Central Americans gathering around 8:00 pm Monday night (0400 GMT Tuesday) in an area called Playas de Tijuana on the Pacific coast, often used by migrants as a departure point for attempts to sneak across the border. After the skirmish, the Border Protection agents detained 25 illegal immigrants while the remainder withdrew back to Mexico after finding a gap in the fence.
The CBP statement said agents had not directly targeted the migrants attempting to cross the fence with tear gas and pepper spray. The agency says it saw members of the group try "to lift toddler-sized children up and over the concertina wire".
Twenty-five of the migrants, including two teenagers, were arrested after making it over the border fence.
Agents responded with smoke, pepper spray and tear gas, it said.
On "America's Newsroom" Wednesday, U.S. Customs & Border Protection (CBP) Deputy Commissioner Robert Perez said the gas was deployed after migrants gathered on the Mexican side began to throw rocks at border agents.
CNN has reached out to Families Belong Together, an advocacy group that works with migrants at the border, but didn't get an immediate response.
"Shortly thereafter, migrants began throwing rocks over the fence at the CBP agents and officers".More news: We Won't Change Our Approach For Manchester City - Liverpool Star
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The Trump administration has defended its use of tear gas against migrants attempting to cross the border, saying it is necessary to stop certain migrants who throw rocks and other projectiles at border agents. The majority of migrants returned to Mexico. "However, this incident needs to be examined within the broader context of United States policies at the border".
Numerous migrants are waiting in Tijuana for a chance to apply for asylum in the USA, but there was a backlog before the caravan's arrival and the wait is expected to be many months.
Under CHP's use of force policy, the incident is being reviewed.
It comes as the U.S. federal government remains shut down as President Donald Trump and Congress argue over funding for his proposed border wall. Hundreds of people downwind of the gas were affected. The federal government began its 12th day of a partial shutdown Wednesday; it is unlikely to end before Congress resumes on January 3.
In a statement, Ms Waldman called on Congress to "fully fund the border wall".