Initial testing of the white powder found in envelopes in a mailroom at a federal building in lower Manhattan reveals a substance similar to Boric acid, according to a senior official familiar with the matter.

Police evacuated 26 Federal Plaza in Manhattan after envelopes containing white powder were discovered Thursday afternoon, officials said.

A possible hazmat incident at 26 Federal Plaza prompted evacuations and a large emergency response in Lower Manhattan on Thursday afternoon after envelopes containing white powder were discovered inside the building, according to city officials.