NEWARK - Officials say two military fighter jets are escorting an airliner from the Canadian border to New York.

Sources tell News 12 New Jersey that an all-clear has been given at Newark Liberty International Airport following a investigation into two suspicious packages inside a UPS sorting facility.

A suspicious package found on a cargo plane in the United Kingdom prompted law enforcement officials to launch investigations into similar packages at Newark Liberty and Philadelphia International airports as well as in New York City.

During a basic security screening process in the United Kingdom, officials found a suspicious item on a cargo plane, according to a U.S. government official who spoke to The Associated Press on condition of anonymity to discuss the ongoing investigation.

UK officials discovered that a toner cartridge on the plane had been manipulated and found wires attached to it, along with white powder. Tests on the device came back negative for explosives, according to a law enforcement official who also spoke on condition of anonymity.

A U.S. official says authorities are investigating whether the string of suspicious packages was a dry run for a plot to send bombs through the mail.

The White House says President Barack Obama was alerted to a "potential terrorist threat." The president is expected to make a statement at 4:15pm.

AP wire services contributed to this report.