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WELD COUNTY, Colo. — At least 29 people were injured after the driver of a flatbed truck fell asleep at the wheel and crashed into a school bus crash in Weld County on Thursday afternoon, the Colorado State Patrol said.

The crash happened near the intersection of County Roads 49 and 24, northeast of Hudson.

Greeley-Evans School District 6 confirmed the bus was coming back from a day trip to Elitch Gardens in Denver. The students aboard the bus were from Greeley Central and Northridge high schools.

The Colorado State Patrol said none of the injuries appeared to be life-threatening. There were 35 people, including 29 students, on the bus.

The Colorado State Patrol said the truck drifted into oncoming traffic and sideswiped the bus, which left the road, rolled and came to rest on an oil and gas site.

Children’s Hospital Colorado in Aurora, Platte Valley Medical Center in Brighton and North Colorado Medical Center in Greeley are treating patients.

Platte Valley has six patients: Four children and one adult in good condition, and one adult in fair condition.

North Colorado Medical Center said it received 17 patients. Children’s Hospital Colorado said it is treating six patients aged 15 to 18 years old. All of the patients at Children’s Hospital Colorado are in good or fair condition.

One patient in serious condition at North Colorado Medical Center was airlifted to another hospital.

A witness who said he helped those hurt in the crash said the bus passengers experienced a range of injuries and that at least two people appeared to have broken bones.

“The kids were all pretty calm for the most part,” the witness said.

Authorities had closed all northbound lanes and one southbound lane of County Road 49. It reopened shortly before 8:30 p.m. Thursday.