Okinawa’s capital Naha plans to evacuate 1,400 people next month as Japanese troops defuse and remove a suspected U.S. bomb from World War II.

According to Naha’s website, the 551-pound munition was discovered last December at the construction site of a sewage system in the city’s Shuri district. Stars and Stripes reported that the Japan Ground Self-Defense Force’s 101st Ordnance Disposal Unit plans to dig 20 feet deep and 10 feet wide around the bomb casing before removing the bomb’s detonator.

According to Stars and Stripes, city and fire officials are responsible for evacuating all buildings within 900 feet of the World War II bomb, including 80 businesses and 470 homes. The evacuation of about 1,400 people is currently scheduled to take place on Sept. 29.

A spokesman for the Naha Disaster Management Department told Stars and Stripes: “We cannot start the measures if there is someone in the evacuation area.”

The spokesman for the Department of Disaster Management stated that the Japanese are currently unable to remove the bomb casing in its current condition because “it is very dangerous as it contains a fuse and could explode.” Stars and Stripes reported that the removal of the bomb was delayed because it was located in a confined area with a large population.

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“We usually build a sort of sand mountain covered with metal plates before removing the hull, but we don’t have the space for that,” the Department of Emergency Management spokesman told Stars and Stripes.

Stars and Stripes reported that city authorities ultimately decided to move forward with plans to dig a hole around the bomb because heavy machinery could not fit in the area around the bomb.

“We have to take many things into account so as not to affect the surrounding buildings. We also have to carry out magnetic surveys again after the excavations,” the spokesman added.

A spokesman for the Self-Defense Force told Stars and Stripes that the defused bomb casing would be stored at a facility on Okinawa until the bomb could be safely detonated at sea.

According to Stars and Stripes, of the 10,000 tons of munitions dropped on Okinawa during the Battle of Okinawa in World War II, about 2,000 tons are still missing.