WASHINGTON -- Segway scooters, touted as almost untippable when unveiled two years ago, are being recalled. It turns out they don't work so well when the batteries get low -- riders have fallen off and been injured.

The Consumer Product Safety Commission announced the recall Friday of all 6,000 scooters that have been sold, saying three people had been hurt. One suffered a head wound and needed stitches.

Commission spokesman Ken Giles said Segway told the agency about the problem.

Segway is offering to install for free new software that will warn when battery power is running down and then will automatically shut down the scooters. Newly built scooters contain the upgraded software.

"We have very high confidence in the safety of the Segway HT and this software upgrade further enhances the safety margins of the machine," Segway said in a statement.

The single-rider, two-wheeled Segway Human Transporters can travel up to 12 mph. Costing $4,950 each, they use gyroscopes to keep upright, making them less likely to fall or be knocked over.

But scooters being operated with low battery power may not have enough juice to remain upright when the rider suddenly speeds up or tries to drive over a bump or up an incline.

The Segway was unveiled in December 2001 to much fanfare by Dean Kamen, an inventor who holds some 100 patents, including a wheelchair that climbs stairs and the first portable kidney dialysis machine.

The U.S. Postal Service has bought 40 of the scooters to test.

For weeks after the Segways were introduced, TV personalities were showing them off on nearly every channel and network.

They got another splash of publicity last summer when President Bush tried one and went flying off at his dad's oceanside compound in Kennebunkport, Maine.

The Segway went down on the president's first attempt, but he stayed on his feet with a leap over the machine. Undeterred, he got on again. His father climbed on a second Segway and they cruised around the driveway at the estate.

The Manchester, N.H.-based company has lobbied states to allow the electric-powered scooters on sidewalks, promoting them as a way to relieve congestion; more than half the states have gone along.

But Jonathan Adkins, spokesman for the Governors Highway Safety Association, which represents state highway safety programs, said there still are safety questions.

Segway "completely rushed these products into cities without adequate consideration as to the impact on public safety," he said. Adkins said there have been no studies on how to safely operate the scooters when they have to share sidewalks with pedestrians and streets with other vehicles.

Commercial and consumer models on the recall list include the Segway HT i167 (i series), the e167 (e series) and p133 (p series).

While Segway plans to contact owners, consumers also may call the company toll free at 1-877-889-9020 between 8 a.m. and 8 p.m. weekdays to obtain the free upgrade. Details also will be posted on the company's Web site at http://www.segway.com.

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On the Net:

CPSC announcement: http://www.cpsc.gov/cpscpub/prerel/prhtml03/03553.html