HOUSTON (AP) — Rep. Gabrielle Giffords was transferred Wednesday to a Houston rehabilitation center, where she began intensive therapy and will have a valve inserted into her breathing tube to help her speak.

Doctors at TIRR Memorial Hermann — The Institute for Rehabilitation and Research — gave few details on Giffords’ treatment or whether she was able to make sounds or speak. Neurosurgeon Dr. Dong Kim did say the congresswoman was making progress at "lightning speed," and Giffords’ ability to swallow safely could mean she won’t need a tube feeding her much longer.

Giffords immediately began physical, occupational and speech therapy Wednesday afternoon, just hours after she was transported from a nearby intensive care unit.

"It’s a busy afternoon already and I anticipate it will be more so in the coming days," Dr. Gerard Francisco, the head of the congresswoman’s rehabilitation team, said at a news conference.

A breathing tube was placed in Giffords’ neck after she was shot in the forehead on Jan. 8 while meeting with constituents in Tucson, Ariz. Six were killed and 13 injured in the rampage in front of a supermarket that apparently targeted the three-term Democratic congresswoman.

Dr. Imoigele Aisiku, director of neurocritical care at Memorial Hermann Texas Medical Center Hospital, said while the congresswoman can breathe independently and swallow safely, the tube cannot be immediately removed because of the length of time it has been in place. Instead, doctors will lessen her dependence on it, a process that has already begun, until it can be safely removed, he said.

Giffords had been in intensive care since her arrival Friday from Tucson. Doctors had said she would remain there until they were able to remove a tube that had been placed in her head to drain excess cerebrospinal fluid. A backup of the fluid can cause pressure and swelling within the brain.

Dr. Dong Kim said the catheter was removed Monday after a scan showed there was no longer a dangerous buildup of fluid.

Precise details on Giffords’ recovery were scant out of respect for the family’s wishes, doctors said. They did not say whether she is able to sit up or stand on her own.

When asked if the congresswoman is able to speak, Kim said "we can say that her speech function, along with everything else, is improving" but declined to elaborate.

Doctors had previously reported that Giffords was having difficulty moving the right side of her body. On Wednesday they described that as "weakness" and said her ability to move had improved.

The transport from the intensive care unit earlier in the day was done under heavy police presence. Helicopters buzzed overhead and police stopped traffic and blocked the road as an ambulance took Giffords and her husband, astronaut Mark Kelly, into the rehabilitation facility. Video from a news helicopter showed a gurney wheeled into the building.

Doctors said Giffords is doing her rehabilitation in her room and not in the hospital’s large gym-like facilities where dozens of patients can undergo therapy simultaneously. She is interacting with the staff and her family and is awake "about as much as you or I are," Aisiku said.

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.