The janitor who found the package alerted administrators, who then opened it and called for help. Personnel from the nearby towns of Lancaster, Clinton, Littleton, and Bolton quickly set up a decontamination tent outside the high school’s main entrance.

Coan, who was joined at a press briefing by the Nashoba regional superintendent and the Chiefs of the Bolton police and fire departments, said that the substance is being handed over to the FBI’s Worcester office, which will perform further testing.

More at source: Boston.com