One person was killed and at least 13 others injured -- four of them critically -- by an explosion that ripped through a busy market in the Pakistani port city of Karachi late on May 12.
Most of the dead and injured are civilians, authorities said.
Police did not initially specify what they thought caused the blast.
But police Deputy Inspector General Sharjeel Karan told Pakistan's Geo TV that they did not have any prior warning or intelligence about the incident.
Initial reports suggested the explosion was centered near a vehicle at the busy Sadar Bazaar belonging to the country's coast guard service.
But that could not immediately be confirmed.
Three Chinese nationals and their Pakistani driver were killed in a suicide attack on April 26 that was claimed by ethnic Baluchi separatists.
They said a woman suicide bomber had targeted the Chinese citizens.