Suffolk County police responded to the Department of Social Services in Hauppauge Friday after a mysterious white powder was found.

Three people were exposed to the substance, police say.

Police originally said the powder was in an envelope, which was opened by a social services employee.

But police later said an investigation determined that the envelope did not contain any substance.

A Suffolk County spokesperson tells News 12 the substance was found on the desk. It was tested and determined to be non-hazardous.

Police say nobody was injured because of the substance.

The nature and source of the white powder is not yet known.