The (Phoenix) Arizona Republic said Gaye Busch was riding in a custom six-person golf cart in a tunnel beneath the speedway when the driver came down a hill and lost control, flipping the cart and injuring five people in the process.
Four people were taken to a nearby hospital as a precaution. Busch refused treatment.
Kurt Busch joked his mother might be the one most likely to get hurt in a crash.
"Don't get in any moving vehicle w/ my mom," Busch tweeted. "She was involved in a crash in the tunnel b4 the end of the race. She will be ok, just a little banged up."