(CNN) Two US soldiers were questioned by Mexican troops earlier this month while conducting a surveillance operation on the US side of the southern border, two US defense officials tell CNN.

"On April 13, 2019, at approximately 2 p.m. CDT, five to six Mexican military personnel questioned two U.S. Army soldiers who were conducting border support operations in an unmarked (Customs and Border Protection) vehicle near the southwest border in the vicinity of Clint, Texas," US Northern Command told CNN in a statement.

"The US soldiers were appropriately in US territory" during the encounter, the statement added.

During the incident, the Mexican soldiers pointed their weapons at the US troops, removing a soldier's sidearm and returning it to the unmarked US vehicle, the officials said.

The Mexican troops were armed with what appeared to be assault rifles, according to one official.

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