(CNN) The driver of the tour bus that crashed in Utah, killing four tourists, was on his first trip with the company, according to the National Transportation Safety Board.

The driver had recently been hired, NTSB investigator Pete Kotowski said during a press conference Sunday.

The driver is back home in California and will be interviewed by investigators in the coming days, Kotowski said.

A blood sample was taken from the driver by the Utah Highway Patrol, but the results have not been processed, he said.

Kotowski said the California-based company that operated the tour bus has been in operation for "a short period of time," and is cooperating with the investigation and has provided any requested documentation.

Investigators will examine the driver's license qualifications and medical history and the company's hiring process, Kotowski said.

The bus was built in 2017 and could accommodate 37 passengers including the driver.

Investigators started interviewing passengers Sunday and will examine the accident scene, bus and environmental factors to determine the cause of the crash, Kotowski said. He did not know how many passengers were wearing seat belts.

A 10-person NTSB team arrived Saturday to begin its investigation, which Kotowski said would take 12-24 months to complete.

Identities released of the four dead

The Utah Highway Patrol identified on Sunday the four Chinese tourists who died in the crash.

Ling Geng, 68; Xiuyun Chen, 67; Zhang Caiyu, 62; and ZhongLiang Qiu, 65, all of Shanghai, were killed when the bus crashed Friday on Utah Highway 12 near Bryce Canyon National Park, the UHP said.

Thirty people, including the driver, were on the bus when it "ran off the road and rolled into the guardrail," the Garfield County Sheriff's Office said in a statement.

Of the 22 people injured in the crash, 12 were still hospitalized Monday, hospital officials said.

Some passengers suffered critical injuries during the crash. CNN has obscured parts of this image because the condition of the victims could not be verified.

Alberto Vasquez, administrator for Garfield Memorial Hospital, said the patients are at Intermountain Healthcare hospitals. Three are in critical condition, 1 is in serious condition and eight are listed in fair condition.

Volunteers helped with translating

A student from Taiwan who attends Southern Utah University helped translate after the crash, reported CNN affiliate KSTU.

"I got a call from the sheriff's office that there is an emergency accident and, 'I need somebody who can speak Chinese to translate for the tourists,'" Jason Chang said. "I know they cannot speak English, so I know they must be really panicked."

Chang told KSTU he spent hours at a hospital helping doctors and nurses communicate with the patients, then assisted law enforcement officers interviewing witnesses.

"They (the bus crash victims) told me they never expected this kind of accident and they just don't know what to do or how to react," Chang said. "Some of them (were) really in pain."

Employees of the nearby Bryce Canyon Resort told CNN their manager was called to the crash scene to assist first responders with translating for the Chinese tour group. The manager is one of the few Chinese speakers in the area, the hotel staff said.

The bus crashed on Utah Highway 12, a few miles west of Bryce Canyon National Park. CNN obscured parts of this image, as the condition of the victims could not be verified.

The Chinese Embassy in Washington said it sent officials to the area to assist the victims.

"We are saddened to hear about the accident in Utah involving a bus carrying Chinese tourists. We are thankful to authorities in Utah for their assistance. The Embassy has initiated its emergency protocols, sent personnel to the area, and will assist the victims as needed," the embassy tweeted.

The wreck was about 7 miles northwest of the entrance of the Bryce Canyon National Park. Bryce Canyon is about 250 miles south of Salt Lake City and just over 40 miles north of the Utah-Arizona border.

Utah's Highway 12 is considered one of the most varied and scenic drives in the country. It connects a number of national and state parks, including Bryce Canyon National Park and Red Canyon on the Dixie National Forest.