A passenger train hit a freight train in Rahim Yar Khan killing at least 19 people on Thursday.
According to reports, 64 people were injured. Some passengers were critically injured.
The speeding passenger train hit the freight train at Walhar Railway Station.
Pakistan army was also taking part in the rescue efforts.
Prime Minister Imran Khan ordered authorities to provide best possible medical care to the victims.
Train accidents are common in Pakistan because of decades of neglect of railway infrastructure.
Last month six people were killed when a freight train collided with a passenger train in Hyderabad.