Migrants run from tear gas launched by U.S. agents, amid photojournalists covering the Mexico-U.S. border, after a group of migrants got past Mexican police at the Chaparral crossing in Tijuana, Mexico, Sunday, Nov. 25, 2018. The mayor of Tijuana has declared a humanitarian crisis in his border city and says that he has asked the United Nations for aid to deal with the approximately 5,000 Central American migrants who have arrived in the city. (AP Photo/Rodrigo Abd)
Migrants run from tear gas launched by U.S. agents, amid photojournalists covering the Mexico-U.S. border, after a group of migrants got past Mexican police at the Chaparral crossing in Tijuana, Mexico, Sunday, Nov. 25, 2018. The mayor of Tijuana has declared a humanitarian crisis in his border city and says that he has asked the United Nations for aid to deal with the approximately 5,000 Central American migrants who have arrived in the city. (AP Photo/Rodrigo Abd) Credit: Rodrigo Abd

San Diego — No criminal charges will be filed against any of the 42 people associated with a caravan of Central American migrants who were arrested in a clash that ended with U.S. authorities firing tear gas into Mexico, The Associated Press has learned.

The decision not to prosecute comes despite President Donald Trump’s vow that the U.S. will not tolerate lawlessness and extensive preparations for the caravan, which included deployment of thousands of active-duty troops to the border.

Rodney Scott, chief of the Border Patrol’s San Diego sector, has said those arrested on suspicion of illegal entry included 27 men; the rest were women and children.

The incident occurred on Sunday at the border in Tijuana, where thousands of caravan members have been arriving in recent weeks after fleeing poverty and violence in Central America. Most of them plan to seek asylum in the U.S. but may have to wait months because the U.S. government processes only about 100 of those cases a day.

As frustrations began to mount over the long wait, migrants marched to the border on Sunday to appeal for the U.S. to speed things up. It turned unruly when four agents were struck with rocks or projectiles and authorities responded by launching tear gas and pepper spray balls to quell the unrest.

But in the end, none of the 42 people had charges brought against them for illegally entering the country or any other counts.

Customs and Border Protection, the Border Patrol’s parent agency, referred only two cases to the Justice Department for prosecution and charges were not filed because the accused had medical problems that prevented them from being held in San Diego’s detention center, according to a U.S. official familiar with the cases who was not authorized to discuss the matter publicly and spoke on condition of anonymity.

Many others were not referred to the Justice Department because they were children or parents accompanying children, the official said. In June, Trump retreated on the administration’s “zero-tolerance” policy on prosecuting illegal entries by generally exempting people who enter the county in families.

The other adults were not prosecuted because Customs and Border Protection didn’t have enough information to pursue charges, including the name of the arresting officers, according to the official, who said it was an extremely chaotic scene.