Nine emergency responders and another employee at Manomet Elementary School were injured, the state Department of Fire Services said. Most were treated at a hospital for burning throats and eyes and released.
Authorities have released few details about the incident. They said investigators are trying to determine if the release of a hazardous substance is related to work being done at the building.
The identity of the dead employee had not been released Monday afternoon.
Jennifer Mieth, a fire services spokeswoman, said testing Monday afternoon found "very low" levels of chemicals at the school.