Investigators scoured two UPS planes at Philadelphia International Airport throughout the day on Friday before finally wrapping up the operation around 6:00 p.m.
Officials tell Action News that a total of six packages shipped from Yemen were removed from the planes there. However, sources tell Action News, no explosives or other dangerous materials have been found in either of the two planes.
A large X-Ray machine, called an HCV Mobile, was being used to scan cargo containers late Friday afternoon. It's made by a company in Pine Brook New Jersey and is capable of examining 25 trucks per hour.
One of the planes came from Paris, France while the other came from Cologne, Germany.
UPS' second largest international cargo processing operation is in Philadelphia with least 80,000 parcels per hour in a 24 hour per day operation.
However, one employee says, those operations were significantly slowed down on Friday because of the terror alert.
Searches of packages also were conducted in Newark, N.J., and New York City. The packages were being sent via UPS.
Intelligence and law enforcement officials discovered suspicious packages in the United Kingdom and Dubai late Thursday night, prompting national security officials to alert President Barack Obama to a "potential terrorist threat," the White House said.
"This certainly does appear to be a widespread probe intended to test our responses and then to plan for the next time," National Security Analyst Ed Turzanski said on Action News.
The intercepted explosives were intended for synagogues in Chicago.
Action News has learned that Philadelphia police have put out an alert to all personnel to pay particular attention and make frequent checks of all Jewish social and government affiliated facilities.
For more on the international investigation, follow this link.
Passengers at Philadelphia International Airport were not affected by this incident.
"I feel secure. I'm sure they know what they're doing," said Bruno Poirer of Newtown, Pa. "Obviously they caught it so, no, it doesn't stress me more."
To check the status of your flight, call 1-800-PHL-GATE or follow this link to the 6abc.com Flight Tracker.