Firefighters responded to a U.S. Customs and Border Protection backup call about three Mexican nationals who were stuck at the top of the border wall near Britannia Boulevard and Britannia Court around 7:30 a.m., according to the San Diego Fire and Rescue Department. Photo via OnScene.TV.

Three people were rescued from atop the U.S.-Mexico border wall at Otay Mesa Monday, but none were injured and all were detained.

Firefighters responded to a U.S. Customs and Border Protection backup call about three Mexican nationals who were stuck at the top of the border wall near Britannia Boulevard and Britannia Court around 7:30 a.m., according to the San Diego Fire-Rescue Department.

Firefighters put up a ladder to help the three climb down from the 30-foot-high security wall.

Officials said it was unusual for migrants to try to climb the wall during daylight. Most attempts occur at night or during heavy fog or rain.

Border Patrol agents confirmed the three people were detained and awaiting processing.

City News Service and OnScene.TV contributed to this article.