Authorities say suspicious package intended for Biden located in Delaware

The package to Biden was considered suspicious due to its similarities to other packages sent this week, law enforcement officials said Thursday. The package was misaddressed and returned to sender, two law enforcement sources previously said.

A manhunt is underway for the perpetrator behind the packages. Law enforcement authorities are treating the series of bombs as a domestic terror matter and are advising the public to remain vigilant.

The motive is unknown, but the recipients are all prominent targets of right-wing criticism and, in many cases, of Trump himself. The package found at CNN’s New York bureau in the Time Warner Center was addressed to former CIA Director John Brennan, city and local law enforcement officials said.

Devices sent to former President Barack Obama, Hillary Clinton, former Attorney General Eric Holder, California Democratic Rep. Maxine Waters and Democratic donor George Soros showed the presence of a sulfur substance, which could have exploded, a law enforcement official said.

The devices are believed to be pipe bombs, inherently unstable, and at risk of being set off just by handling.

The FBI’s counterterrorism division is leading the investigation Thursday into the packages and the agency says it’s possible additional packages were mailed to other locations.

At the White House, Trump vowed Wednesday that “we will spare no resources or expense” to pursue the perpetrator.

CNN’s Susannah Cullinane, Karl de Vries, Pamela Brown, Sarah Westwood, Josh Campbell, Jessica Schneider, Brynn Gingras, Mary Anne Fox, David Shortell, Brian Stelter, Eli Watkins, Mary Kay Mallonee, Sonia Moghe, Elizabeth Landers and Dan Merica contributed to this report.