NEW YORK -- 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 -- and in at least one incident, break some teeth.
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.
Segway has received six reports of problems with the Personal Transporter, resulting in head and wrist injuries. The vehicles were previously known as the Human Transporter.
Segway is offering a free software upgrade that will fix the problem. The upgrades will be done at Segway's 100 dealerships and service centers around the world, according to Segway spokeswoman Carla Vallone, and the company based in Bedford, N.H., will pay to ship the devices to the appropriate center if need be.
It is the second time the scooters, which sell for about $4,000 to $5,500, have been recalled since they first went on sale in 2002.
Segway chief technology officer Doug Field, who has been involved with the development of the device since its earliest days, said the problem that sparked the latest recall was found while the company was testing its new model. He said a very unusual and specific set of conditions can cause the problem.
The scooter's speed is determined by how far forward the user leans, and if the rider leans too far forward, a "speed limiter" pushes them back to keep the device at its maximum speed of 12.5 mph. The problem happens after the speed limiter tilts back, the rider steps off the device and then gets back on it quickly.
Field said the actions that would cause the problem are of "very low probability, but possible, which then made us go pull every reported accident in the company's history." After the company found the six incidents believed to be related to the problem, it notified the CPSC and got the ball rolling on the recall, Field said.
Field and Segway Chief Executive Jim Norrod would not comment on whether the problem has sparked any lawsuits, and would not give any details about the severity of the injuries sustained.
According to CPSC spokesman Scott Wolfson, the injuries included broken teeth, a broken wrist and facial injuries including one that needed surgical repair.
"Any injury is too much to us," said Norrod.
Segway's dealers have received the software updates and owners can schedule an appointment through the company's Web site to have the update installed.
"We're ready to start upgrading immediately," said Norrod.
The company last month launched a new generation of the Segway that allows users to steer the device simply by leaning in the direction they want to go, rather than using a small wheel on the handlebar. All new shipments will have the corrected software.
Norrod, who was brought in as Segway's CEO last year by the company's principal investors, Credit Suisse Group and the venture capital firm Kleiner Perkins Caufield & Byers, has made grooming the company for an initial public offering or sale of the company a top priority. He said there has not been a negative reaction to the recall from the dealerships that sell Segways.
"We don't see that it will have a negative impact on business at all," Norrod said.
The most famous tumble from a Segway came in 2003, when President Bush tried one out at his family's estate in Maine. The device went down on his first attempt, but Bush stayed on his feet with an awkward hop over the scooter. He quickly got back onboard and was soon cruising around the driveway on the Segway.