New Year, same old issues.

US border agents have reportedly fired tear gas into Mexico to push back against what one official called a "violent mob" of migrants as they rushed the US-Mexico border near Tijuana.

Reuters reports that clouds of the noxious gas could be seen wafting up from around the fence at the border. One migrant picked up a canister and threw it back into U.S. territory.

More than 150 Central American migrants approached an area of the border in Tijuana in the Playas neighborhood near the beach late on Monday.

Migrants said they thought security measures might be relaxed due to the New Year’s holiday. U.S. security personnel fired tear gas into Mexico after midnight as some migrants prepared to climb a border fence, according to the Reuters witness. During a second attempt, migrants began to pass youths and children over the razor wire along the fencing to the U.S. side. U.S. Department of Homeland Security spokeswoman Katie Waldman called the group “a violent mob” and said they had thrown projectiles at agents who responded with “the minimum force necessary to defend themselves.” “Congress needs to fully fund the border wall,” Waldman said in a statement.

U.S. Customs and Border Protection (CBP) said in a statement the gas was aimed upwind of people throwing rocks on the Mexican side who obstructed agents from helping the children being passed over razor wire.

CBP said most of the migrants attempting to cross returned to Mexico while 25 people, including two teenagers, were detained.