A tour bus crash near Bryce Canyon National Park in southern Utah left at least four dead and numerous people injured Friday, authorities said.

A bus driver and 30 Chinese-speaking tourists were headed to Bryce Canyon National Park late Friday morning when the bus rolled off the road on State Route 12 and crashed into a guardrail, according to the Garfield County Sheriff's Office.

Sheriff James Perkins said all of the occupants were adults, with no children on board.

Here is what we know now:

4 people were killed, many were injured

The four deceased, all Chinese nationals, were Ling Geng, 68, Xiuyun Chen, 67, Zhang Caiyu, 62 and Zhongliang Caiyu, 65, according to the Utah Highway Patrol.

All four were residents of Shanghai.

Five people remained in critical condition Saturday, a day after the crash. They were being treated at Dixie Regional Medical Center in St. George. Five others at the hospital were in serious condition, while another had been discharged.

At Utah Valley Hospital in Provo there were two patients listed in serious condition, according to a spokesperson for Intermountain Healthcare.

All 31 people on the bus at the time of the crash were hurt. Some in the bus were not wearing seat belts.

The bus had been headed into the park as part of a tour but began to veer off the road for an unknown reason, according to the Utah Highway Patrol. The driver overcorrected and the bus tipped over, rolling over once, hitting a guardrail and landing halfway off the road.

Chinese translators were needed

Shortly after the crash, Utah Highway Patrol tweeted, "We are confirming the tourists are Chinese speaking tourists" and a reverse-911 message was sent to residents in Garfield County and other surrounding areas in Utah asking if Chinese-speaking translators would be available to help at the scene.

Officials with Southern Utah University, a college in Cedar City about 90 minutes from the crash scene, asked international students from China to help as translators.

In a tweet, the Chinese embassy in the U.S. thanked Utah authorities and wrote, "The Embassy has initiated its emergency protocols, sent personnel to the area and will assist the victims as need."

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California company owns the bus

The bus that crashed is registered to company called America Shengjai, in Ontario, California.

America Shengjai operates two buses, according to the U.S. Department of Transportation. It's unclear which of the two buses crashed.

Both buses are limousine-style coach buses built in 2016 and 2017, according to a Carfax.com report on the vehicle identification numbers.

Neither bus has been involved in any crashes or cited for major safety violations, according to the DOT.

The National Transportation Safety Board said on Twitter that a 10-member team will arrive at the crash site on Saturday to investigate the accident.

NTSB will coordinate with Utah Highway Patrol, but UHP also will conduct its own investigation, according to NTSB on Twitter.

Bus crashed mere miles from park entrance

The bus crashed at mile marker 10 on State Route 12 at about 11:30 a.m., according to the the Garfield County Sheriff's Office. That's about 10 miles from the park entrance.

About Bryce Canyon National Park

Bryce Canyon National Park is located in southern Utah, about 130 to 140 miles in driving distance from St. George (depending on your route) and about 270 miles in driving distance from Salt Lake City.

Tour buses are a common sight at Bryce Canyon, with tours often starting in Las Vegas or Salt Lake City and also visiting nearby national parks like Zion and the Grand Canyon.

Bryce Canyon, though less heavily visited than Zion, hosted 2.7 million recreational visitors in 2018, according to the National Park Service.

Contributing: David DeMille; Lexi Peery; Robert Anglen, The Arizona Republic; Bree Burkitt, The Arizona Republic; Joel Shannon, USA TODAY; and The Associated Press