Live World War II-era anti-tank round found near US-Mexico border fence

Border agents patrolling near the U.S.-Mexico border fence last week came across an unlikely sight: a live, unexploded World War II-era ammunition round.

The agent, who was assigned to the Brian A. Terry Station in Bisbee, Arizona, found an unexploded MKII 37mm ordnance round, U.S. Customs and Border Protection said Tuesday.

A safety perimeter was set up around the ordnance round and an airman with the Explosive Ordinance Disposal Unit from Davis Monthan Air Force Base responded to the scene Tuesday.

After confirming it was a live round, the airman detonated it in place.

The MK2 37 mm round was used by the 37 mm Gun M3, the first dedicated anti-tank gun fielded by the U.S. and first introduced in 1940. It became the standard anti-tank gun of the U.S. infantry as its size allowed for it to be pulled by a jeep.

The U.S. Army used the 37 mm anti-tank gun M3 during World War II, primarily in the Pacific.  (U.S. Army)

However, it was rendered ineffective in the battles in Europe because of the rapid improvement of German tanks and, by 1943, it was gradually replaced by the more powerful British-developed 57 mm Gun M1. It remained in service until the end of the war in the Pacific.

It’s unclear how the ammunition round ended up at the border fence.

Lucia I. Suarez Sang is a Reporter for FoxNews.com. Follow her on Twitter @luciasuarezsang