Wreckage from the detonation of a World War II shell in Biak, Indonesia, in May. Indonesian National Police

In May, a group of fishers on the Indonesian island of Biak were dismantling an unexploded shell left over from World War II when the device went off, reportedly killing seven people and injuring 19 others. Officials have concluded that the fishers were harvesting materials from the shell for use in blast fishing.

Biak, a small island, lies off the coast of New Guinea, which was the site of intense fighting between Allied forces and Imperial Japan. Heavy bombing and naval battles left behind a host of unexploded bombs and artillery shells, which are still being uncovered by fishers, farmers, and construction workers.

On nearby Wakde Island, bombs may emerge from the ocean at low tide or explode in the forest during heat waves, according to Sonya Martha Kawer, an archaeologist with the National Research Center for Archaeology in Indonesia.…