A spokesman for the grocery store told German news agency DAPD that the supermarket remained closed to ensure customer safety.
He said experts were "frantically" working to track down the creature, though there had still been no trace of it.
Staff from the zoo in Neunkirchen are at the scene, and zoo director Norbert Fritsch said the risk is not to be underestimated if the arachnid in question was, indeed, a banana spider.
He said the spider's bites can be life-threatening, even for a healthy adult. Banana spiders can grow to be 13 centimeters in size. The term refers to two genera of spiders, one of which is large but relatively harmless, and another highly venomous species.
The police in Homburg said the spider had been hiding in a case of bananas. It escaped when supermarket employees were unpacking the delivery.
The spider reportedly scurried under a shelf and then disappeared. Pest control specialists were notified, and the store was evacuated.