CRJ-900 Flight Attendant reported during taxi that two separate passengers each had a bag that contained lithium ion batteries; and both were checked baggage. The flight crew then returned to the gate to remove the bags; the passengers; and refuel.

Narrative

Everything was going smoothly; we had pushed back from the gate and did our demo. After the demo; the aft Flight Attendant came to the front of the aircraft and told me that a passenger had said they had lithium batteries in their specially tagged bag. I asked if it was a large black backpack; and they replied yes. I alerted the flight deck and we returned back to the gate. During boarding a man had a large black backpack that didn't fit into the overhead bins. I remember asking him if he had any lithium ion batteries; medications; or electronic devices in his bag and he replied no. The bag was specially tagged. I later learned that aft Flight Attendant had also asked this man the same question. After arriving back at the gate a woman said that her checked; white tagged bag has a drill in it with the portable drill chargers - not attached to the drill - the wireless battery kind that hold a charge. I alerted the flight deck. Both of these bags were eventually taken off the plane and the passengers along with them. It took over an hour for the bags to be taken off as there was a lot of back-and-forth with if they needed to be taken off the plane with the rampers; Tower; and gate agents. The Captain wanted them off. We also needed to re-fuel as we were about to take off when we learned about this problem and needed to do the gate return; so we were underweight and 3 more passengers were boarded.