The bus that killed multiple people in a collision on westbound Interstate 10 at milepost 173 south of Ahwatukee on Friday morning should not have been in operation, according to the U.S. Department of Transportation Federal Motor Carrier Safety Administration.

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The company that operates the tour bus, Tierra Santa Inc., lost its ability to operate April 1, 2009, because it does not have insurance, according to a statement released Friday afternoon.

In all, six people -- four women and two men -- died after the bus rear-ended a pickup truck, swerved off the roadway and rolled at about 5:30 a.m., said Bart Graves, a spokesman for the Arizona Department of Public Safety. Several people were ejected, with at least one landing 25 yards away.

Helicopter footage showed luggage scattered across the area.

"The bus is in shambles," Graves said.

There were also two minor collisions related to the bus crash, and several fender-benders on I-10 eastbound, Graves said. One person in a sedan was hospitalized with serious injuries.

A triage location was set up off I-10 to treat the injured, and five medical helicopters were dispatched to airlift people to area hospitals. Ten more people were transported to hospitals by ambulance.

"Numerous fire agencies and EMS responded to the scene to triage all the patients we had," Graves said.

There were two drivers and 20 passengers on the bus, and all have been accounted for. In all, 16 people, ages 11-76, were injured.

One of the drivers, who is 66 years old, was taken to Scottsdale Osborn and is cooperating with investigators, Graves said. He is a Mexican national, and he has a California driver's license.

Maricopa Medical Center is treating eight of the accident victims, said medical center spokesman Michael Murphy. Six patients are in critical condition, one is serious and an 11-year-old boy is in good, Murphy said.

"We're seeing some blunt force trauma injuries typical of a car crash," Murphy said. "We're seeing broken pelvises, broken spines, head injuries, lacerations -- so our trauma team has been very busy this morning."

Trauma surgeon, Dr. Marc Matthews said the medical center was alerted early this morning of the mass casualties. Matthews said the patience arrived about 5 minutes apart from each other. "At some point you just wonder when it's actually going to stop. And we were fortunate that it's just eight and wasn't thirty-eight," said Matthews.

Because most of the patients spoke only Spanish, Matthews said translators were a crucial part of the trauma team. It also helped because they were alerted to the crash and incoming casualties right around shift change.

"We had people staying who were on call last night and people just coming on. So we had fresh hands and some people who were ready to go home, but were willing to stay extra. And that's what you do. You pitch in," said Matthews.

Second Bus Crash In 2 Years For Company

Alex Porras said his sister, 25-year-old Jasmine Porras, was coming back from a two-week vacation in Mexico when the bus crashed Friday morning. She was critically injured.

"I was shocked when I got the call," a red-eyed Porras told The Associated Press at Maricopa Medical Center. "We're really worried."

Alex Porras, 28, said his sister, who is married, had just graduated from Arizona State University with a nursing degree and was hoping to start working soon so she could help others.

Graves said DPS is in contact with the Mexican consulate to notify families of those killed and injured; names of those involved won't be released until the families have been told.

Additionally, investigators with the National Transportation Safety Board are going to "touch base" with DPS investigators, Graves said.

The bus appears to have driven from central Mexico, crossed the border in El Paso, Texas, and was headed to Phoenix to switch drivers. The bus' final destination was Los Angeles.

This is the second bus crash in two years for Tierra Santa, according to the Department of Transportation Web site. The first crash resulted in no injuries, but the bus had to be towed.

In the past two years, the company's had three vehicle inspections, according to the Web site.

One of the buses was inspected in Texas in August 2009, and inspectors found that the driver did not have proof of insurance and the company did not have the authority to operate, inspectors said in their report.

The bus had issues with lighting, headlamps and emergency exits, inspectors said. The driver did not speak English and neither the driver nor the passengers could provide identification.

In total, inspectors found eight violations.

A second inspection occurred in New Mexico in September 2009. The bus was cited for not having proper lights.

CBS 5 News Reporter Donna Rossi contributed to this story.