BROOKLYN - Police say a suspicious letter with a white powder found at Brooklyn Federal Court has been deemed non-toxic.

Authorities say it was found at around 4 p.m. in Brooklyn Federal Court at 225 Cadman Plaza. They say the letter had the word ‘anthrax’ on it, prompting a temporary lockdown of the building’s first floor.

Police told News 12 that an employee in the clerk's office opened the envelope. Three people were exposed to the substance and decontaminated as a precaution. They refused further medical attention.

Investigators have not yet determined what the substance is or if it posed any health risks.