(CNN) A bomb smuggled into a market inside a carton killed as many as 31 people in northern Pakistan Friday, according to officials.

The explosion, in Kalya in Orakzai Agency, took place just before 9 a.m. local time (10.30 p.m. ET Wednesday), according to Khalid Iqbal, police deputy commissioner in Orakzai. The majority of the dead were Shia, he added.

The blast took place in the vegetable section of the market, Iqbal said.

At least 51 people were injured, 17 critically, according to Amin Ullah, the District Administrator for Kalaya. They have been moved to the larger towns of Kohat and Peshawar via ambulance, Ullah said.

No group has yet claimed responsibility for the attack.