YUMA, ARIZ. (AP) A construction crew in southern Arizona has discovered an unexploded howitzer round while working on a road.

Yuma Proving Ground's explosives experts identified the ordnance as a 155 mm howitzer round of a kind that were used in World War II and the Vietnam War, The Sun reported.

The round found on Martinez Lake Road during an $18 million improvement project that began in February was the second discovered this year. The first was found in April in the same location.

Martinez Lake Road was closed for several hours while crews worked to remove the round, authorities said.

Both rounds "were found more than one mile outside of YPG's boundaries, and have nothing to do with the proving ground's present-day testing," Yuma Proving Ground Spokesperson Mark Schauer said.

The area was once part of the Desert Training Center, also known as the California-Arizona Maneuver Area, which was established in 1942 to train U.S. forces in desert warfare, officials said.

The area stretches 18,000 sq. mi. across the outskirts of Pomona, Calif., east to within 50 mi. of Phoenix, south to the suburbs of Yuma and north into the southern tip of Nevada.

The center was operational for two years, where 13 infantry divisions and seven armored divisions trained.

The road project is expected to be completed in April 2021.

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