A police department spokesperson said one of the 57 people injured appeared to be in critical condition.
"People were thrown into the air and onto the ground," passenger Elizabeth Banta told CNN. "There were definitely many people on the ground who were not moving."
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A "public-spirited" passerby retrieved the child.
A man wanted in connection with a hit-and-run crash which killed a four-year-old girl has been arrested, police have confirmed.
Scotland's First Minister was pictured with her feet up on the sofa while penning the document to Theresa May.