Migrants run as tear gas is thrown by U.S. Customs and Border Protection agents to the Mexican side of the border fence after they climbed the fence to get to San Diego from Tijuana, Mexico.
Customs and Border Protection, the agency that oversees, the Border Patrol, said the tear gas and pepper spray fired this week were aimed away from the women and children along the border line, and directed specifically at the group of rock-throwers.
Migrants who spoke with AP said they arrived in Tijuana last month with the caravan from Honduras.More news: OH police agencies send condolences after hilarious tweet about doughnut truck fire
Border Patrol agents added that the group tried to lift toddler-sized children over the concertina wire, but agents were unable to help the children because too many rocks were being thrown.
The agency also said 25 migrants were detained while others crawled back into Mexico through a hole under the fence.
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.
As U.S. immigration authorities have slowed admissions for asylum seekers, thousands of caravan migrants have lingered in Tijuana waiting for a chance to present themselves at ports of entry or, in some cases, cross the border illegally.More news: 6 people injured at BWI Airport from partial jet bridge collapse
A larger group initially approached the border, but at least a third turned back when they saw the presence of Border Patrol officers.
In November, after a group of migrants tried to rush the border, McAleenan defended the use of tear gas: "As the events unfolded, quick, decisive and effective action prevented an extremely unsafe situation".
Tijuana has become a flashpoint in the debate over U.S. immigration policy, which has been intensified by the recent deaths of two migrant children in United States custody and a partial USA government shutdown over President Donald Trump's $5 billion demand to lawmakers for a wall along the border with Mexico. The deployment of tear gas will be reviewed by CBP's Office of Professional Responsibility, the agency said.More news: Germany: Drugged Driver Forces Car Onto Airport Tarmac
The migrant caravan left Central America in October and travelled 4,300km (2,600 miles) to Tijuana in the hope of reaching the United States and requesting asylum. The stalemate has led to a partial government shutdown.