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.

The 41-floor office building is home to ICE's New York City field office, as well as the FBI's New York field office and an immigration court. It has made headlines and been the site of frequent protests over ICE operations in the city amid the Trump administration's crackdown on undocumented immigrants.

Suspicious white powder that forced the ICE field office in New York City to evacuate is not hazardous, the FBI said Friday.