A workman attaches cables to a passenger bus after the bus crashed through a guard rail on Highway 75, Friday in Sherman, Texas. Authorities say a Vietnamese-American Catholic group on the way to a religious festival honoring the Virgin Mary was riding on an illegally operated charter bus, which blew a tire and skidded off a highway early Friday, killing 15 people and injuring more than 40.

Sherman, Texas ? An unlicensed charter bus carrying a Vietnamese-American Catholic group on a pilgrimage to a religious festival blew an illegally treaded tire and skidded off a highway early Friday, killing at least 15 people and injuring dozens, authorities said.

The bus, en route from Houston to Missouri with 55 people aboard, smashed into a guardrail and tipped over along the edge of the road at about 12:45 a.m., crushing one side of the vehicle and scattering luggage, clothes, a sandal and a blood-soaked pillow across the grass and pavement.

Ten people were taken to the hospital by helicopter, and some were in critical condition late Friday.

Passenger Leha Nguyen, 45, said passengers were dozing off when she heard a noise and screaming, and opened her eyes.

“Somebody was laying on my legs. A lady next to me, she had her arm crushed up. The lady who was on my left, a man was on top of her,” she said at a hospital. She said nobody had been wearing seat belts, and people were strewn all over. A television had fallen on one person.

“I think I’m the luckiest one out of most people,” she said.

Most of the passengers were from the Vietnamese Martyrs Church and two other mostly Vietnamese congregations in Houston. They were on their way to Carthage, Mo., for an annual open-air festival honoring the Virgin Mary.

The Marian Days pilgrimage, begun in the late 1970s, attracts thousands of Catholics of Vietnamese descent and includes a large outdoor Mass each day, entertainment and camping at night.

“Please pray for us,” said Holly Nguyen, a 38-year-old church member who was following behind the bus in a car but did not see the wreck. She anxiously awaited word of her father, who was on the bus when it ran off the road about 65 miles north of Dallas, close to the Oklahoma line.

The right front tire, which blew out, had been retreaded in violation of safety standards, said Debbie Hersman, a member of the National Transportation Safety board. The tread had separated from the tire itself in a process called delamination.

“If there is a loss of pressure or the tire becomes delaminated, it’s much more difficult to control the vehicle,” she said.

It is legal to retread such tires but not on the axle that steers the bus, Hersman said. The driver was a 52-year-old who had a commercial license but whose medical certification had expired, she said.

The driver was reported in stable condition.

The bus operator, Iguala BusMex Inc. of Houston, had applied in June for a federal license to operate as a charter but was still awaiting approval, according to online records.

The company recently filed incorporation papers, listing the same owner and address as Angel Tours Inc., which was forced by federal regulators to take its vehicles out of interstate service June 23 after an unsatisfactory review, records show. Details of the review were not in the online records.

Neither entity is currently authorized to operate as a carrier in interstate commerce, said John H. Hill, administrator for the Federal Motor Carrier Safety Administration.

“We have requested law enforcement agencies to be alert for any buses being operated by Angel Tours or Iguala BusMex, since they are not authorized to operate legally,” he said in a written statement. “If found on the road, we want law enforcement to immediately stop and place the vehicles out of service.”

In a Houston building with a weathered Angel Tours plywood sign, a man declined to identify himself Friday or comment to The Associated Press about the wreck.

The tragedy was the nation’s deadliest bus crash since 2004, when 15 people were killed in a wreck in Arkansas on their way to Mississippi’s casinos. In 2005 near Dallas, 23 people were killed when a bus carrying nursing home residents away from Hurricane Rita caught fire while in bumper-to-bumper traffic.