"Initial investigations show that it was a time-controlled device on a motorbike which was the cause of the blast," Rana Arif, spokesman for Lahore police, told news agency AFP.
The blast that shattered windows of nearby shops and buildings took place at the Paan Mandi in Lahore's famous Anarkali market, where Indian commodities are sold.
There was no immediate claim of responsibility, but there have been a series of blasts and attacks against police since December when a truce between the government and Pakistan's Taliban lapsed.
Condemning the blast, Prime Minister Imran Khan urged authorities to provide the best medical facilities to the injured. He also sought a report from the Punjab government.
RHM/PR