HOUSTON (AP) -- Police stood guard as an ambulance took Rep. Gabrielle Giffords from intensive care to a rehabilitation hospital in Houston on Wednesday, an encouraging step that came after doctors upgraded her condition from serious to good.

Doctors at Memorial Hermann Texas Medical Center Hospital determined the Arizona congresswoman was healthy enough to move to nearby TIRR Memorial Hermann, where she will continue her rehabilitation work.

Helicopters buzzed overhead and police stopped traffic and blocked the road as an ambulance took Giffords and her husband, astronaut Mark Kelly, a short way to TIRR, which stands for The Institute for Rehabilitation and Research.

Video from a news helicopter showed a gurney wheeled into the building.

Giffords had been in intensive care since her arrival Friday from Tucson, Ariz.

Last week doctors placed a tube in her head to drain excess cerebrospinal fluid. A backup of the fluid can cause pressure and swelling within the brain.

Doctors said Friday that Giffords would stay in the ICU until the tube was taken out because of a risk of infection. Her move Wednesday suggests that the tube might have been removed, which would be another good sign in her recovery.

Giffords was shot in the head Jan. 8 in a rampage that killed six people and injured her and 12 others. The three-term Democratic congresswoman was hit in the forehead while meeting with constituents outside a Tucson supermarket.

The alleged assassination attempt cast a somber mood over President Barack Obama's State of the Union speech on Tuesday night, where many lawmakers in both parties wore black-and-white lapel ribbons to signify the deaths and the hopes of the survivors. Giffords' husband watched the speech from her bedside in Texas, as he held her hand.

The 22-year-old suspect in the shootings, Jared Loughner, pleaded not guilty Monday to federal charges of trying to assassinate the congresswoman and two of her aides. He also faces federal murder charges in the deaths of a federal judge and a Giffords aide, and more charges were expected.