Neighbors and rescue personnel tried to stop a speeding car that plowed through a crowded street festival and threw children out of its path, preventing more serious injuries, Mayor Adrian M. Fenty said Sunday.

Only one of the 40 people struck by a woman's careening Volvo Saturday night remained hospitalized the next day, officials said.

"I can't believe that we're actually saying that right now, everyone is going to pull through," Fenty said. He credited "some unbelievable heroism" by citizens and rescuers.

The driver, Tonya Bell of Oxon Hill, Md., was treated for an ankle injury and was in police custody pending arraignment Monday, police said. She was preliminarily charged with aggravated assault while armed. The "armed" designation is because she used a vehicle.

Authorities believe Bell was going about 70 mph when she tore through Unifest, a church-sponsored street festival in southeast Washington. Witnesses described a scene of mayhem after Bell sent people and strollers flying, leaving debris and injured bodies strewn in her path.

A 4-year-old boy with a broken leg was still hospitalized, but was expected to be discharged Monday, said Emily Dammeyer, a spokeswoman at Children's National Medical Center.

Marcellus Jackson's father saved the boy's life by throwing him out of the way of the speeding car, Fenty said. The father, Vincent Hayes, was then hit by the speeding car head-on but was OK.

"The car just passed so fast, and all of a sudden I just heard people screaming," said the boy's mother, Denise Jackson. "I turned around, and it was like bodies falling out of the sky."

Some questioned why Bell was not stopped after she was seen driving erratically and striking an unmarked police cruiser 20 minutes before the rampage. Police Cmdr. Patrick Burke said officers had followed Bell's 1991 Volvo, but were told to stop because the traffic violation did not pose a threat to officers. They responded after people were struck.

Officials were still waiting for toxicology results, but Burke confirmed that some witnesses said Bell may have been smoking something and laughing as she drove through the crowd.

Bell had a 7-year-old girl in the car with her whose identity wasn't released. The child was not injured and was taken by Child Protective Services.

Burke said additional charges expected Monday would likely include assault on a police officer while armed. Two police officers working at the festival were thrown off their motor scooters when they drove in front of the car in an attempt to stop it. They suffered minor injuries.