JAKARTA, Indonesia (AFP) — A suspected shell left over from World War II exploded under a stilt house in an Indonesian fishing village, killing five people and wounding nearly 20, police said Monday.

The blast in Indonesia’s restive eastern Papua region startled locals with a thunderous boom on Sunday afternoon, emitting a ball of flames followed by a thick smoke column, according to footage broadcast on Kompas TV.

Nine homes were destroyed.

“The source of the explosion is strongly suspected to have been a bomb or mortar left over from World War II,” Papua police spokesperson Cahyo Sukarnito told Agence France-Presse.

Three people are still recorded as missing, but Cahyo said several body parts have yet to be identified.

At least 19 people were treated for minor injuries, he added.

“We will provide further updates once the search for victims and the investigation have been completed,” said Cahyo.

Last year, nine civilians were among 13 people killed in West Java province when an explosion occurred as Indonesian troops attempted to dispose of rejected munitions by detonating them in a pit.

Indonesia was a major battle zone during WWII when Japanese forces occupied what was then the Dutch East Indies, and Allied forces fought to retake control.