Authorities said at least two dozen people remain missing and hundreds of families have been left without shelter following days of intense rainfall.
"We unfortunately have 16 more confirmed bodies, bringing the total to 20. And we have two dozen missing," Troche told state broadcaster Bolivia TV.
He added that at least 300 people had been rescued by helicopter and some 2100 families were so far affected around the River Pirai.
Heavy rains began early on Saturday, according to the National Meteorology and Hydrology Service.
One survivor, visibly shaken, described being trapped until neighbours reached her.
"I kept shouting until they heard me, but then we couldn't do more. We went to the road but couldn't pass," Saturnina Quispe said.
Video footage showed a river bridge giving way under the sheer force of floodwater while crews moved in with heavy machinery to clear debris and try to restore vital access to affected communities.
Officials expect weather conditions to improve in the coming days, aiding rescue efforts as water levels recede.
Meteorologists warned about the combined effects of El Nino and La Nina weather patterns, which are generating heavier rainfall in the Amazon basin.
Bolivian President Rodrigo Paz, who took office last month, met with experts, cabinet members and scientists to assess the situation.
He criticised past administrations for leaving the state without sufficient resources to respond to emergencies and also pointed to widespread deforestation over the past two decades as a factor worsening the floods, noting Bolivia lost 10.4 million hectares to fire in 2014 - the worst wildfire crisis in its history.
"This is not over, it's just beginning," Paz told reporters.
25°C