The federal government on Friday said the company that owns the bus that crashed near Yucaipa, killing eight people, an immediate hazard to public safety and ordered it to shut down immediately.

"Safety is our number one priority, and we will not tolerate unsafe bus conditions on our nation's roads," said U.S. Transportation Secretary Ray LaHood in a statement. "We will not allow safety to be compromised."

The order comes five days after the bus, owned by Scapadas Magicas Tours, based in National City near the Mexican border, crashed and rolled over on Highway 38 on its way back from Big Bear Lake. The crash killed seven of the passengers and the driver of a pickup that collided head-on with the bus.

More than 20 others were hurt, some critically.

The trip was to go from from Tijuana to Big Bear Lake and back.

Regulators say a post-crash investigation of the company's two other buses that had been operating in the U.S. found serious mechanical safety violations. The buses were immediately placed out of service.

Inspectors say the company also failed to have its vehicles regularly inspected.

The company failed 36 percent of its safety inspections in the past two years, according to federal transportation records.

Those records showed that 25 of the company's vehicles had been inspected over the past two years but only 16 passed inspection, exceeding the national average failure rate of 21 percent, according to the Federal Motor Carrier Safety Administration.

The company is based at a small office in an industrial office park in National City, southeast of San Diego.

On Friday, no one answered the door at the office. A sign directed deliveries to the property managers' office. A representative of the property owner said Scapadas Magicas would not be commenting and asked journalists to leave.

None of the company's two other buses were visible at the office park, nor were National Transportation Safety Board officials or law enforcement personnel.

The order comes on the heels of calls from Sens. Barbara Boxer and Diane Feinstein for stronger bus safety regulations in a letter to LaHood.

The letter, dated Feb. 7, asks LaHood to coordinate closely with the National Transportation Safety Board to develop stronger regulations.

California's two U.S. senators, both Democrats, wrote in the letter that the "greatest tragedy of Sunday's accident is that it was not an isolated incident."

They said that since 1990, there have been more than 180 motor coach crashes and fires, which have killed 334 people and injured more than 3,000.

The NTSB is investigating the crash. While the cause is not known, witnesses said mechanical problems could have been a factor.

The senators' letter was called "right on target" by Brenda Knight, niece of Fred Richardson, 72, of Mountain Home Village, who died from injuries sustained when the bus plowed into his Ford pickup truck east of the Mill Creek Ranger Station.

"If you read this letter, it looks like it has been a problem for a long period of time now," she said. "There are some companies out there that have high standards and really good ones, but it appears (Scapadas Magicas Tours) is not one of those."

In addition to Richardson, the seven other fatal victims of the crash were: Guadalupe Olivas, 61, Elvira Garcia Jimenez, 40, and Victor Cabrera Garcia, 13, all of San Diego, and Aleida Adriana Arce Hernandez, 38, Rubicelia Escobedo Flores, 34, Mario Garcia Santoyo, 32, and Liliana Camerina Sanchez Sauceda, 24, all of Tijuana.

A number of those injured in the crash remained hospitalized on Friday.

One adult female was at Arrowhead Regional Medical Center in Colton. Another adult female was discharged Thursday afternoon, and an adult male was discharged Friday.

No update on five victims, one a girl, at Loma Linda University Medical Center was available on Friday.

Staff photographer Gabriel Luis Acosta contributed to this report.