Defence Minister Ernesto Justiniano said in a statement 14 people were missing.
The blast occurred about 2.30pm on Friday in an area used to store pyrotechnic material, authorities said.
While the cause has not been established, officials said the blast originated in the defence ministry's fireworks stockpile.
Earlier, Viacha health director Rita Nebraska told local television between 10 and 15 people were believed to have died in the incident.
She said 62 people had been injured.
Fourteen of those were transferred to hospitals in La Paz, including a girl with third-degree burns, she said.
Police said more than 50 people were injured and dozens of homes damaged, largely by windows shattered in the blast.
Ambulances, medical teams and police were deployed to the military complex to assess the damage and evacuate the wounded to health centres.
Nebraska said firefighters had warned that a heat source remained at the site, raising the risk of another explosion, and urged residents to stay at least 150m away.
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