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.

Mayor Eric Adams said he was aware of the situation unfurling at 26 Federal Plaza and New York Fire Department hazmat teams were on site to ensure safety.