Effective October 1, 2008, medium lithium batteries become fully regulated for air shipment in the U.S. Department of Transportation's (DOT) Hazardous Materials Regulations. Lithium batteries are considered a hazardous material because they can overheat and ignite in certain conditions and, once ignited, can be especially difficult to extinguish.
The new regulation will require packages containing medium lithium batteries, and offered for air transport, to be properly packaged, marked, and labeled as Hazardous Materials and accompanied by shipping papers. Otherwise, the shipment may be delayed, or significant U.S. DOT fines could apply. U.S. DOT has the ability to issue fines and penalties as high as $110,000 per violation for non-compliance.
Evidently, your shipper made a mistake that has delayed the package.