TUCSON, Ariz. — A bus filled with Mansfeld Magnet Middle School students stopped for reasons Friday while taking those students home.
Tucson Unified School District officials say a group of students were playing with an unknown substance.
TUSD director of communications say "One of the students threw a substance back onto the bus. The bus driver then stopped the bus, contained everyone, and called school safety and asked them to come out and help investigate."
Tucson Police and Tucson Fire were also called to scene. They tell us the call was for something that looked like it could be mercury.
After doing some investigating officials determined the material to be gallium.
It's a non-toxic substance used in chemical labs.