Police said on Saturday that potholes were caused by the blasts near Gaddo Chowk, which is why trains were forced to stop at different station.
Rangers and police arrived at the scene and started gathering evidence. A search was launched for the arrest of suspects.
The bomb disposal squad said that the blast was carried out by a non-electric device and that explosives weighed 150 grams.
A railways official, speaking with SAMAA TV, said that no casualties took place. He added that the traffic was restored after 90 minutes.
A three-kilogram bomb was recovered from the same area few days ago. APP