Police in Hai Phong detained three explosive dealers on Thursday for destroying up to 40 houses and injuring dozens of people.
Police arrested Nguyen Van Lam, 45, his son Nguyen Van Don, 24, and their neighbor Ngo Van Hieu, 24, all local residents.
The trio was carrying 124 kilos of homemade dynamite and 1,000 fuses through the area when they encountered local authorities on Tuesday night, police said. The three men stashed the dynamite in a ditch, police said.
They returned to their merchandise in the middle of the night, police have charged. In an effort to cover their tracks, the men set fire to the explosives.
Police have recommended that prosecutors charge the three with "keeping and transporting explosive materials illegally" and "damaging others' property."
Do Huu Ca, deputy director of Hai Phong police, said that the explosion in the remote mountainous area did not constitute a terrorist attack. There seemed to be no malice aforethought, Ca said.
Authorities are still analyzing the composition of the explosive which they have said is not TNT. They have estimated that the accused detonated hundreds of kilos of the material.
Vu Van Tung, 24 year-old resident, said that the blaze began at around 3 a.m. while people were asleep. A big blast followed the flames, throwing him into the wall of a house.
"I woke up several minutes later and the power was all cut."
Tung said gates of several houses were thrown into the middle of the road. The village ditch had been reduced to a giant crater, he said.
Bui Thi Yen, 51, another resident, said that broken bricks and roofing tiles rained down on her two grandchildren, a three year-old and a five month-old baby, causing injury to their heads, arms and legs.
The blast shattered glass doors nearly two kilometers away, residents said.
Local authorities have given VND150 million (US$7,900) in relief to victims.
Residents said no such incident has ever happened in their peaceful farming village.
Since last year, 11 cases of illegal explosive production and trafficking have been discovered by local police.