General Manager of the Pakistan Railways Asad Saeed said Wednesday that broken track joint might have caused the train derailment in southern Pakistan.
State-run PTV quoted Saeed as saying, "A welded track joint broke. Tracks shrink in winter. There are many forces on the track and sometimes this joint breaks."
Giving probable reasons behind the tragic accident, Saeed ruled out possibility of terrorism.
The railway tracks are old and the government is in the process of replacing them, he added.
Saeed said that an investigation had been ordered to ascertain cause of the accident.
He said that search and rescue activities were continuing and aid workers were struggling to cope with rising number of casualties.
He assured that the accident did not affect the arrival and departure of other trains.
Meanwhile, at least 58 were killed and more than 120 others were injured in the train accident in Pakistan's southern Sindh province early Wednesday morning.
Traveling from southern port city of Karachi to eastern border city of Lahore, the Karachi Express, with some 900 passengers heading home for the Islamic holiday of Eid ul-Adha, derailed near Mehrabpur, some 400 north of Karachi, at about 2:25 a.m. (2125 GMT Tuesday), according to local press reports.
Railways officials confirmed that 15 out of the 17 carriages of the train derailed and two of them were destroyed completely in the accident.
President Pervez Musharraf Wednesday directed immediate inquiry into the causes leading to the derailment of the Karachi Express and the heavy loss of life.
Musharraf directed the Pakistan Railways to investigate into the matter and fix responsibility so that the culprits may be punished and measures taken to ensure such incidents do not recur.