The United States closed its busiest border crossing with Mexico on Sunday, November 25, after Mexican police broke up a protest of Central American migrants massed in Tijuana, scattering some demonstrators toward the border where US officers hurled gas canisters from the American side.
Traffic in both directions was suspended at the San Ysidro port of entry between San Diego and Tijuana, the US Customs and Border Protection agency said on Twitter.
US President Donald Trump has raised alarms about a caravan of Central American migrants as it approached the United States, with its members planning to apply for asylum on reaching the United States.
On Sunday, hundreds of caravan members, including women and children, were peacefully protesting when they were stopped by Mexican authorities, who told them to wait for permission.
As the morning wore on, and it became clear they would not get permission, people started to express frustration.
A small group broke off and headed a few hundred feet (meters) away to a part of a canal between Tijuana and San Diego that led to the border fence.
At that point, before the group had reached the border, US Customs and Border Protest officers who had gathered on the other side of the fence launched canisters of what a Reuters reporter said felt and smelled like pepper.