"At least 24 people were killed - we have identified 16 bodies," Phu Tho policeman Pham Quang Minh told AFP, raising the number of dead from 21 in Saturday's incident.
Minh said more than 20 people had been injured, lower than the near-100 initially reported to have been hurt in the explosion at a military complex in northern Vietnam.
"According to a preliminary investigation, some explosives self-ignited in storage, which caused a fire and further explosions at the site," he said, adding both fireworks and other explosives were stored at the Z121 military facility.
Plumes of black smoke billowed from the complex, around 120 kilometres (75 miles) north of Hanoi, as fireworks exploded uncontrollably for several hours on Saturday before the blaze was contained.
The explosion prompted the evacuation of some 2,000 people living near the area, most of whom had returned by Sunday.
Minister of Defence Phung Quang Thanh visited the area late Saturday, calling for urgent assistance for the victims' families.
In the hours after the explosion local hospitals were swamped with victims, some with horrific burns. The most critical cases were moved to a specialist burns centre on the outskirts of Hanoi.
In 2010, fireworks being prepared at Hanoi's My Dinh stadium for use in the city's 1,000th anniversary celebrations exploded, killing three foreigners and one Vietnamese national.
Handmade firecrackers were traditionally used as a symbol of good luck to celebrate the Lunar New Year - known locally as Tet - and at weddings.
But, in 1994, the government banned the production and use of all firecrackers nationwide for safety reasons, changing instead to fireworks - which are produced only in state-approved facilities.
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