Fourteen Mexican Army soldiers were briefly detained and then returned to Mexico after crossing into the United States over a border bridge in El Paso, Texas. Two Mexican military vehicles crossed the bridge linking El Paso to Ciudad Juarez early Saturday morning, U.S. Customs and Border Protection (CBP) said in a statement.

CBP explained that the soldiers, their weapons and equipment "were secured for security and processing purposes" and noted that the military elements said "they did not realize they had entered the United States. One of the soldiers "received a civil penalty after CBP agents discovered in his possession a quantity for personal consumption of marijuana," according to Customs and Border Protection (CBP).

The 14 soldiers, their equipment and vehicles were returned to Mexico a few hours after Mexican military officials went to pick them up. Photographs posted on social media show about six Mexican Army soldiers in full tactical gear sitting next to a lane of a border bridge. It was not clear if they were handcuffed.

Mexico's Defense Ministry did not respond to a request for comment at this time. Elements of the Mexican military have crossed the border unnoticed on other occasions, but it usually occurs in areas where the border is not clearly demarcated, not at major border crossing bridges.

El Diario de Juarez reported that some people documented the detention of the soldiers, between 00:00 and 00:20 hours, with photographs they took with their cell phones. The photos show a green van with an official number a few meters from the CBP checkpoints, which was surrounded by U.S. federal police vans.

Other photos show the soldiers lined up, secured by CBP agents. The newspaper reported that videos posted on Facebook show the moment in which the U.S. authorities subdued the soldiers.