The blast happened in Multan district, some 350 kilometers from provincial capital Lahore.
District Coordination Officer (DCO) Zahid Salim Gondal told reporters that initial reports suggest the blast took place after the explosives carried by one of the passengers in the auto-rickshaw went off.
"Ball bearings have been recovered from the blast site indicating that it might be a suicide blast. It seems some one in the three-wheeler was carrying explosives and it exploded after hitting the motorcyclist," he said.
District Emergency Officer (Multan) said at least 10 people have been killed in the blast and 50 others suffered injuries. Some 20 of the injured are in critical condition, Gobdal said.
Rescue officials shifted the injured to the Nishter Hospital Multan where the condition of a dozen of them is stated to be critical.
Prime Minister Nawaz Sharif condemned the blast and expressed grief over the loss of lives. He also expressed solidarity with the victims' families.