The deaths occurred after a brawl broke out during a middle school graduation party and someone detonated the tear gas, sending more than 500 people rushing for the exits, said Interior and Justice Minister Nestor Reverol.
In comments aired on state VTV television, Reverol put the death toll at 17.
Witnesses said a minor, one of seven people detained in the incident, is suspected of setting off the tear gas.
Official reports said the victims died of suffocation or multiple trauma. At least five people were hurt in the incident and taken to hospital for treatment.