The blast occurred in bogie number six of the economy class, near the Chichawatni railway station, while the train was on its way from Peshawar, ANI reported.
The injured were admitted to a nearby hospital.
On January 30, a blast targeting the Jaffar Express injured eight passengers and derailed two bogies in the Kachhi district of Balochistan.
In another recent explosion, at least five people were injured near Quetta Police Lines area, with the Tehreek-e-Taliban Pakistan (TTP) claiming responsibility for the attack, stating that security officials were the targets.