RENO, Nev. -- Something went wrong with an experiment at a Nevada children's museum and it set off a minor explosion.

Officials say something went wrong with a smoke tornado demonstration. It caused a small explosion and 7 children and 2 adults were injured.

Officials say they suffered minor to moderate burns, mostly to their hands, arms and faces.

Four others were hurt, but were treated at the scene.

"It was just a demonstration that the museum does on a regular basis, and it malfunctioned, and at this point, we're investigating why it malfunctioned, and the specifics of the event," said fire chief Michael Hernandez.

Staff members were teaching children how to make a chemical tornado using ethyl alcohol and boric acid.