Consumers should stop using the device immediately and contact the company for a free software upgrade, according to the U.S. Consumer Product Safety Commission, which is working with Segway on the recall. The Bedford, N.H.-based Segway said no hardware changes are required.

A commission spokesman said Segway received reports of six incidents that involved facial and wrist injuries. One user required facial surgery and another was hospitalized overnight. Others suffered broken teeth, he said.

"A condition has been identified in which the Segway PT can unexpectedly reverse the direction of the wheels which can cause a rider to fall," the company said Thursday. "This can occur when the PT's Speed Limiter tilts back the machine to slow it down and the rider goes off and then back onto the PT within a short period of time."

The voluntary recall applies to all Segway PTs sold to date, including all Segway PT i Series, e Series, p Series, XT, GT and i2 models. The Segway x2, due for release later this month, is not affected by the recall. All new shipments of the I2 are being shipped with the new software release, the company said in the statement.