A321 ground personnel reported a bag with a lithium battery sticker affixed to it was found while loading the aircraft. Loading was stopped and the bag was removed for further investigation.

Narrative

Upon loading Aircraft X on [Gate] XX; Crew Chief came across bag with lithium battery UN3481 sticker affixed to the side of the bag. All loading stopped and a manager was called over to investigate the situation further. Crew Chief went inside break room to reverify no DG (Dangerous Goods) planned and no DG paperwork in the system. Bag was held off to the side until the contents could be verified and subsequently removal of improper markings. All bags loaded flight departs after short maintenance delay. I saw a DG sticker and stopped all work until more information could be gathered from reverifying the DG list for the day to Company Management tracking down passenger.Many failures across the system could have contributed to this incident. From the time the bag was checked; ticket counter failed to look at the bag and see the sticker and proceed to ask follow-up questions in regard to its meaning. Any number of bag room individuals would have had to handle this bag as well. We all receive the same training of if you see something say something but that was not the case - bag loaded into cart and brought to gate.Manager notified. DG page verified.Suggestion: Disciplinary action against all parties and departments that did nothing to stop undeclared dangerous goods traveling in baggage. The Ramp Crew Chief should be the first person to report incident with so many hands and eyes on said bag before Crew Chief is loading aircraft.