The driver of a sport utility vehicle packed with suspected illegal immigrants flipped over while trying to elude federal agents, killing nine people and injuring 12, officials said.

Five of the injured, including a pregnant woman, were hospitalized in critical condition in Yuma and Phoenix, most with head trauma.

Five people were pronounced dead along the road Monday while four others died at Yuma Regional Medical Center, according to the U.S. Border Patrol. Three men and six women died.

The Chevy Suburban was carrying 21 people — all Mexican citizens — when the driver tried to circumvent a checkpoint on the highway more than 30 miles north of Yuma, according to authorities.

With Border Patrol agents in pursuit, the driver attempted to make a U-turn and rolled over, Border Patrol spokesman Lloyd Frers said.

Yuma County Sheriff's Maj. Leon Wilmot said the vehicle was traveling faster than the posted speed limit of 50 mph at the time of the accident.

The car had swerved to avoid a spike strip put out by Border Patrol agents, Wilmot said. Border Patrol spokeswoman Agent Veronica Lozano said she didn't know whether agents put out the device.

The Yuma County Sheriff's Office was investigating the crash, while Immigration and Customs Enforcement was investigating immigration-related aspects.

Scores of illegal immigrants die each year while crossing the Mexican border into Arizona, many in car crashes. Smugglers often flee from authorities at high speeds or overload vehicles, which makes them difficult to control.

Nationwide, at least 291 illegal immigrants have died during border crossing attempts from Oct. 1 through Sunday, Border Patrol spokesman Gustavo Soto said. That includes 75 deaths due to heat exposure, 45 drownings, and 42 motor vehicle incidents.

The Yuma area, a sandy stretch of desert in southwestern Arizona, has become one of the nation's busiest immigrant-smuggling hotspots. President Bush visited the area in May as part of his push for a sweeping overhaul of immigration laws.