By Kim Glovas and Walt Hunter

PHILADELPHIA (CBS) - The FBI is investigating the theft of a large sum of money from a plane that landed at Philadelphia International Airport Thursday morning.

The plane, with a shipment of $96 million on board, according to authorities, flew into Philadelphia from Dallas at 10:25 a.m. Thursday. The money was being transferred from the Federal Reserve Bank in Dallas to the one in East Rutherford, New Jersey. Once the plane arrived at PHL, the money was placed inside an armored truck and then taken on the three-hour drive to the bank.

“When the money finally arrived at East Rutherford, they discovered that the packages had been opened and some money was missing,” said the FBI’s Frank Burton Jr.

Sources say a total of $20,000 was discovered missing. The packages were all 100-dollar bills that were not supposed to be distributed publicly until next year. He says they are very distinct, with a large gold “100′ on the back, lower right hand side.

He says on the front there is an orange “100″ on the lower right hand side, and a shape which looks like an orange jar next to Franklin’s head. It’s actually a Liberty Bell.

Authorities are trying to determine how and when the money was taken. A search for the suspect(s) is underway.

If anyone sees these bills, they should call the FBI at 215-418-4000.