LOS ANGELES, Sept. 20 -- Four Chinese tourists died and over 20 were injured in a tour bus crash near Bryce Canyon National Park in the U.S. state of Utah on Friday, according to the Utah Highway Patrol (UHP).

A total of 31 people were on the bus including the driver. All 30 passengers are Chinese nationals, according to the update of the UHP on Friday night.

"Four have been killed, 12-15 with critical injuries and 10 more with minor to serious injuries," the UHP tweeted, later adding that the driver is a Chinese American and one of the injured parties.

"We are working with the Chinese Embassy to assist the passengers as well as make notification to families in China," the UHP added.

Currently, five of the injured are in critical condition, with several more with very minor to serious injuries in stable condition, said UHP.

The crash occurred before Friday noon on the state road 12 (SR-12), about 5.6 km west of Bryce Canyon, according to authorities and staff of the park.

According UHP, the tour bus was eastbound on SR-12 heading towards Bryce Canyon. The bus drifted off the road to the right. The driver overcorrected to the left and the bus rolled over, during which it landed on a guardrail and then came to rest on its wheels blocking the westbound lane.

The Chinese Embassy in the United States said the bus was carrying a Chinese tour group into Bryce Canyon in Garfield County.

The embassy said in a statement that it has been in touch with local police for further details regarding the accident and has dispatched an emergency team to provide assistance for the victims.

Three helicopters were dispatched and multiple agencies were involved, said the Garfield County Sheriff's Office.

A video footage acquired by Xinhua showed the top of the white bus was smashed with one side peeled away. The footage was shot by a Chinese tourist on a bus passing by the scene. Screams and sighs could be heard in the video.

The UHP said multiple air ambulances and rescue crews have been dispatched.

The injured have been taken to area hospitals throughout southern Utah, and several were transported by an air ambulance, according to the UHP.

The National Transportation Safety Board, an independent U.S. government agency responsible for civil transportation accident investigation, tweeted Friday afternoon it was launching a team to investigate the crash.

Garfield County Commissioner Leland Pollock told media that he felt terrible for those involved in the crash.

"This is pretty overwhelming for a little county of 4,900 people. This is just horrible for us," he was quoted by U.S. media as saying.

Some victims were treated at Garfield Memorial Hospital in Panguitch City, Utah, according to media reports.

The hospital tweeted Friday night it has received 19 patients so far, among whom 11 have been transferred, one admitted and seven discharged.

"I grieve with all who lost loved ones in this crash and I'm grateful for the quick work of first responders, as well as all those who are volunteering to act as translators," Utah Governor Gary Herbert tweeted.

Bryce Canyon National Park in southern Utah is known for its unique geology, according to the National Park Service website.