A female employee had handled the package just moments before the accident. She sent it down a chute and was about six feet away when it exploded. The worker reported a flash and a smell like gunpowder but nobody was hurt.
The explosion happened when lithium batteries came into contact with each other, according to San Diego police Capt. Jim Collins.
However, FedEx spokesman Rob Boulware says the batteries were nickel-cadmium.
Collins said the FedEx facility should reopen for business later today. Boulware says the only damage was to the package, and FedEx is working to identify the shipper.