MANHATTAN, New York (WABC) -- Envelopes containing a white powder that were found at a government building in New York City housing an Immigration and Customs Enforcement office did not contain any dangerous substances, officials said Friday.

The incident occurred Thursday afternoon at 26 Federal Plaza, in Manhattan's Foley Square, New York City Mayor Eric Adams said .

26 Federal Plaza is the New York headquarters of federal law enforcement agencies, including the FBI, Homeland Security and ICE.

The five letters were found at about 4 p.m. in the mailroom of the ICE Enforcement and Removal Office on the ninth floor, according to the FBI.

Initial testing on Friday showed that the substance was a boric acid, commonly used in pesticides and other chemicals. It can be harmful if eaten.

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