A 500-pound bomb from World War II dropped by the United States on Japan exploded at a Japanese airport after nearly 80 years.

One bomb out of the 179,967 tons of bombs dropped on Japan during World War II was buried underneath a Japanese runway for decades, having landed on the Miyazaki Airport when it was being used by the Imperial Japanese Navy. The bomb was discovered Thursday morning local time, prompting a response from emergency services. It suddenly exploded for unclear reasons.

This photo taken from a Kyodo News helicopter shows part of a damaged taxiway at Miyazaki Airport in southwestern Japan, Wednesday, Oct. 2, 2024, after an explosion was reported. (Kyodo News via AP)

No casualties or damage to aircraft were reported as a result of the blast, though it delayed about 80 flights, according to Japanese Chief Cabinet Secretary Yoshimasa Hayashi, CBS News reported.

An investigation by the Japan Self-Defense Forces and law enforcement found that the bomb was a 500-pound U.S. bomb. The reason as to why it suddenly exploded is being investigated.

A video of the explosion was published on social media.

Hundreds of undetonated bombs dropped on Japan by the United States Army Air Force remain buried across Japan.

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After the effective destruction of the Imperial Japanese Navy and Air Force in battles from 1942 to 1945, the U.S. was given free rein to wage a massive bombing campaign to force Japan to surrender.

The strategic bombing campaign was one of the largest in history, destroying Japan’s industrial capacity and playing a key role in forcing the country to surrender on Aug. 15, 1945. Hundreds of thousands of people were killed in the bombings, most through deadly firebombing raids. Some estimates go as high as 900,000 people.