FBI Agent Steve Emmett said Friday a bomb tech unit and other investigators are at the scene of PureTalk, an electronics refurbishing company.
Covington Police Capt. Ken Malcom said the powder was released when an employee pulled apart two batteries that appeared fused together. The employee and others reported burning eyes, skin irritation and numbness in the hands.
He said the package also included a note stating that the intent was to harm someone.
Newton Medical Center spokeswoman Linda Moseley said the 10 were being treated, but there was no update on their status.