Segway has recalled all 23,500 of its electric scooters to fix a software glitch that can topple users off the platform and that has caused six head and wrist injuries.

The problem can unexpectedly shift the wheels into reverse, causing riders to fall off, the US Consumer Product Safety Commission said yesterday. The Commission advised all users to stop using the devices until upgrading the software.

With a starting price of $4,000 (about £2,125), the self-balancing scooter has seen slow sales for simple recreation, but its ability to cruise at 12mph for 24 miles on each battery charge has made it popular with golfers, police officers and urban tourists.

Companies such as City Segway Tours of Paris offer guided tours on rented scooters, cruising the streets of Atlanta, Chicago, New Orleans and Washington DC as well as Budapest, Paris and Vienna. Yesterday that company sought to reassure its customers, posting a statement that every machine in its fleet had already been updated, and that its tour schedule would continue without interruption.

Likewise, workers at San Francisco Electric Tour Company, which offers Segway tours of San Francisco and Sausalito, California, said they had scheduled the upgrade to be completed by the end of the day.

"It hasn't affected us because it's such a freak thing," said Lawrence Sylou-Creutz Ojermark, a company spokesman. "It's like those mobile phone batteries that can catch fire. There was a recall for those a couple years ago, but how many people do you know whose mobiles actually exploded?"

The recall affects all Segway PTs (Personal Transporters) sold between March 2002 and September 2006, including the PT i167, i170 and i180, the e167 and p133, and the XT (cross-terrain) and GT (golf) models. Segway can fix the problem with a free software upgrade, CEO Jim Norrod said in a statement. He asked all users to visit the company's website.