Emergency Situations Ministry spokesman Viktor Beltsov said 78 people sought medical care and 66 of them were hospitalized. None of them was assessed as being in life-threatening condition.
He said all those sickened had been at one branch of the Maksidom home-goods chain.
In two other shops of the same chain, suspicious canisters connected to wires and possibly containing gas were found, and customers were evacuated.
Russian media had unconfirmed reports that the canisters had been set up with timing mechanisms to go off as time bombs.