A number of similar crude explosive devices have been sent since Monday to former President Barack Obama, Hillary Clinton, other top political figures and CNN's New York offices.
Here is a timeline:
A suspicious package was sent to the Florida office of Democratic Rep. Debbie Wasserman Schultz on Wednesday morning. It was intended for former US Attorney General Eric Holder but had the wrong address. The package was returned to the Democratic congresswoman because that was the return label on the package, two law enforcement sources said.
CNN's New York bureau in the Time Warner Center was evacuated shortly after 10 a.m. Wednesday after the discovery of a package containing a bomb, said law enforcement officials, who added that the package was addressed to former CIA Director John Brennan. Brennan has appeared on CNN.
A suspicious package intended for California Democratic Rep. Maxine Waters was intercepted at a congressional mail screening facility in Maryland, sources told CNN.
A package containing a possible explosive device intended for former President Obama was intercepted by the US Secret Service at a screening facility in Washington.
A package containing possible explosive device and intended for Hillary Clinton was intercepted. It was discovered during routine mail screening procedures Tuesday evening, according to authorities.
A suspicious package targeting billionaire investor and philanthropist George Soros was rendered safe in Bedford, New York, a law enforcement source told CNN. Bedford police said they received a call about 3:45 p.m. Monday reporting a suspicious package found in a mailbox. The package appeared to be an explosive device, police said.