A car ran a police checkpoint and rammed into a building where President Bush had just finished a speech Saturday morning in northern Mississippi.
The president was in no danger during the breach of security, the Secret Service said. A woman was pulled from the car by a swarm of law enforcement officers and taken to the DeSoto County Sheriff's office along with children who were in the vehicle with her.
Although the incident ended peacefully, the possibility that the car could have contained explosives made it a serious breach of security and raised questions about the failure of authorities to head off the vehicle.
The woman was identified as Betina Mixon, 29, a local resident, according to a law enforcement official who spoke on the condition of anonymity.
Ann Roman, a spokeswoman for the Secret Service, said the woman taken from the car was charged with trespassing and aggravated assault on a law enforcement officer and was in custody Saturday evening. No federal charges had been filed, but officials were continuing the investigation.
Federal officials were "very confident" that the women did not intend to threaten the president, Roman said. No weapons were found on her or in her car, Roman said.
A law enforcement official said the woman appeared to have mental problems.
"Essentially, she was trying to locate her mother-in-law, who was attending the president's speech," William Jenkins, the FBI's acting special agent in charge in Jackson, told Associated Press.
Just minutes after the incident, the president and his motorcade left the DeSoto Civic Center and headed to nearby Memphis, Tenn., where he boarded Air Force One and continued with the rest of a campaign trip.
Witnesses said Bush had just finished his speech about 10:25 a.m. local time when a dark gray Toyota Camry ran a police checkpoint and headed toward the civic center.
The driver ignored commands from police to stop, Roman said. The car drove across the large, vacant parking lot surrounding the arena as numerous motorcycle officers followed and other security personnel ran toward the driver with guns drawn, according to reporters who witnessed the incident. The car appeared to be going about 30 mph.
The driver hit a curb, the tires blew out and the car crashed into the Civic Center, a law enforcement official said. Police surrounded the car, dragged the driver out and slammed her to the ground, according to Mark Walz, a CNN cameraman who recorded the scene.
The woman struggled -- kicking and dragging her legs -- as she was led away and hustled into the back seat of an unmarked white car.
Roman said that three children were passengers in the woman's car.
In Washington, a law enforcement official said the woman was being interviewed by the Secret Service, which is responsible for protecting the president, and local police.
It wasn't immediately clear what kind of barriers secured the area or how the car got past them. But questions were raised about whether police or the Secret Service should have acted to stop the car before it reached the civic center.
Bomb-laden cars and trucks have caused destruction and death around the world, from Oklahoma City to the Middle East.
The car struck the Mississippi building about 50 to 70 feet from the exit ramp where Bush's limousine was to emerge.
"With the world turmoil we're in today, with car bombs and what have you all over the world, anytime something like this happens you've got to be concerned about it," said Hamilton Brown, a former Secret Service officer who guarded presidents from John F. Kennedy to the first President Bush.
Brown said the only ways to intercept a car whose driver refuses to stop are to blockade it with another car, stand in front of it or attempt to shoot the driver.
Any such action could trigger explosives if they were in the vehicle. If there were no explosives, the driver might be needlessly killed or wounded.
"It's a judgment call," Brown said. That the driver in this instance had children in the car likely "weighed a little bit" in the decision not to shoot, he said.
It is very difficult to disable a car by shooting at it, he added, and doing so could have risks as well.
"If this woman wanted to be a martyr and she had the car full of dynamite and then you shoot it and the whole thing blows up, then what?" Brown said.
The security breach occurred about 10 minutes after Bush had delivered a spirited campaign speech urging Mississippi residents to elect Washington lobbyist Haley Barbour as governor Tuesday.
The president spoke to about 9,000 Republicans who showered him repeatedly with ovations.
As Bush arrived at the civic center, his motorcade was greeted by several dozen protesters holding signs such as "End Bush's War," "Drop Bush, Not Bombs" and "Fire Bush."
Bush kept to his schedule, appearing at two events in Kentucky to campaign for Rep. Ernie Fletcher (R-Ky.), who is running for governor.
The president's fourth and final stop was in Gulfport, Miss., again on behalf of Barbour, a former chairman of the Republican National Committee.
Bush did not mention the incident during a brief speech on Fletcher's behalf to thousands of Republicans gathered in a sweltering hangar at the Barkley Regional Airport in Paducah, Ky., his first stop after the Mississippi incident.
Chen reported from Southaven and Shogren from Washington, D.C.