HUDSON, Colo. (CBS4) – A 36-year-old man has been issued a summons for careless driving after police say he fell asleep at the wheel before causing a school bus crash on Thursday afternoon. The crash happened just north of Hudson in Weld County and left dozens injured.

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William Carroll, of Littleton, was driving a truck near County Roads 22 and 49 right before the crash. The impact when his truck hit the school bus sent both vehicles off the road.

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The bus, which was carrying as many as 40 people, rolled over on it side.

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The bus was bringing a group of Greeley Central High School students home from a trip to Elitch Gardens in Denver. A few of the crash victims remained in the hospital Friday morning.

(credit: CBS)

The bus driver suffered a broken arm.

(credit: CBS)

Witnesses say workers from a nearby oil well rushed to the scene to help the students after the crash.

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“I saw a bunch of kids laying on the ground, the guys from Noble Energy helped them out, and I just saw thousands of ambulances pulling in and out of this place,” said one witness.