Seminole High School was placed on lockdown during first period on Tuesday to allow substances brought to school as part of a chemistry assignment to be checked before being carried into the building.
According to the sheriff's school resource deputy, certain chemistry class students were assigned to bring in a substance from the Periodic Table of the Elements.
Hazmat crews examined the substances. No chemicals or substances were spilled, and nobody was hurt, according to the Pinellas County Sheriff's Office.
Other than mercury - which was contained in a thermometer - I have no further information at this time about what substances were actually brought to school by the students.