CNN employees have returned to their offices in New York City, hours after authorities found a potentially lethal explosive had been sent to the facility located in upper midtown Manhattan.

“The NYPD has concluded its security sweep, and it is now safe to return to the building<‘ said CNN Worldwide President Jeff Zucker in a memo to staff. ” I so appreciate your patience, as I know what a long day this has been for all of you.”

The suspicious package found inside CNN’s mailroom in New York forced the evacuation of its headquarters on Wednesday, coming just hours after the Secret Service reported finding packages sent to former President Barack Obama and former Secretary of State Hillary Clinton and her husband, former President Bill Clinton.

The package at the CNN headquarters “appeared to be a live explosive” and contained wires and pipe, James O’Neill, the NYPD commissioner, said at the press conference. The package contained an envelope containing white powder, he said.

The package was removed from the building by authorities and was being taken to a screening facility. The package was mistakenly addressed to John Brennan, the former CIA director, who is a contributor to MSNBC, not CNN.