A bomb weighing nearly 500 kilograms was found Saturday on a barge that had taken sand from the Mekong Delta's Hau River.
Workers on the barge belonging to Can Tho resident Le Van Banh said they were "frightened" as the bomb appeared while they were pumping sand from the barge to the ground.
The bomb was 170 centimeters high and 30 centimeters in diameter.
Banh said the sand had been taken from the Hau River in Dong Thap Province and taken to Can Tho on Friday night.
He said this was the third time a bomb from the river ended up on his boat. Around a month ago, they found a 300-kilo bomb.
In September, authorities in the delta's Bac Lieu Province also discovered 10 bombs left over from the Vietnam War in construction material storehouses.
The officials said the bombs must have been taken from the Hau River when barges dredged for sand. The unexploded ordnance are all still equipped with active fuses.