NEW YORK CITY ? Segway Inc. is recalling all 23,500 of the self-balancing scooters it has shipped to date because of a software glitch that can make its wheels unexpectedly reverse direction, causing riders to fall off.

The U.S. Consumer Product Safety Commission, with whom Segway is cooperating on the voluntary recall announced Thursday, said consumers should stop using the vehicles immediately.

It is the second time the scooters have been recalled since they first went on sale in 2002.