The substance was later found to be boric acid, a chemical which can irritate the skin, cause shortness of breath if inhaled and lead to vomiting if ingested.

Officials say the substance found Thursday in envelopes in the mailroom of an ICE office at 26 Federal Plaza was not hazardous.

26 Federal Plaza was evacuated after the substance was found inside envelopes in the mailroom.

Brooklyn public school student Mamadou Diallo has been detained by ICE, according to New York City Councilmember Lincoln Restler.

A Brooklyn high school student has been detained by ICE, marking the third arrest of a New York City public school student by immigration authorities in recent months.