Seven students and a teacher from a middle school in the Altai Territory were hospitalized following the poisoning by an unidentified gas.
The ministry said that on Wednesday at 10:00 a.m. local time (7:00 a.m. Moscow time), students at School No. 1 in the village of Komsomolskoye smelled a sharp odor. Thirteen students and a teacher suffered from reddening of the eyes and sore throats.
"The possible cause of the poisoning by an unidentified gas in middle school No.1 could be a child's prank," a spokesman for the emergencies department said. "Presumably, one of the children sprayed mace (tear gas), which resulted in the adverse reaction."
In all, 185 people have been evacuated from the school, and a group of experts from the Ministry of Emergency Situations continues to investigate.
Earlier, the ministry reported that 13 students and two teachers had complained of the effects of the gas.