The passengers said that the driver of the bus, heading from Fort Abbas and Faisalabad, started to race his vehicle with another bus.
A truck appeared in front of the Faisalabad-bound bus as he was overtaking the second bus and the vehicle overturned near Faqirwali when its driver lost balance while trying to avoid it.
Rescue teams arrived at the scene after being informed of the incident. The wounded persons were rushed to a local hospital for treatment.
Four people are said to be in critical condition, sources said.