A bomb was found aboard a Chicago bound UPS plane that originated from Yemen, according to CNN.
The bomb was discovered after the plane had landed in London and was reportedly altered to look like a printer cartridge.
Flights containing suspicious cargo have been grounded in Newark and Philadelphia as well for investigations.
Update: John Brennan, Deputy National Security Adviser for Homeland Security and Counterterrorism, told reporters that the packages containing the material was addressed to synagogues in the Chicago area.