Neither chemical is classified as toxic, Tuoi Tre News reported.
The toys, manufactured in China, are shaped like grenades. If they are stepped on or hit hard, the two substances combine to produce carbon dioxide, which expands, producing a small explosion.
Children who played with them reported a sharp smell and 37, all students at Chu Van An Primary School in Dak Song, developed symptoms that included chest pain and trouble breathing. All were quickly released from a hospital, but the symptoms recurred in some of the children and they had to be hospitalized again.
The children reported buying the grenades from a store near their school for 5 cents each. Police have seized the store's entire supply.