The Punjab Mail which was on its way to Mumbai derailed near Sampla-Kharawar at 3.50 AM, Alok Mittal, the IGP of the Rohtak Range, said. The accident site is over 70 kms from Delhi.
Six bogies of the second-class sleeper compartment (S-5 to S-10), one luggage compartment and the guard coach jumped tracks, railway officials said, adding five of the coaches overturned after the derailment.
Three passengers received grievous injuries in the incident while 24 others escaped with minor ones. All the injured passengers were shifted to PGIMS hospital at Rohtak.
Commissioner Railway Safety, Northern Circle, R K Kardam will hold a statutory inquiry into the accident.
Preliminary information indicates that the derailment has been caused prima facie because of rail fracture.
Railway officials said that at least 50 metres of the rail track was found broken at the accident site.
"We are trying to ascertain whether the railway track broke due to the accident or whether the broken track led to the accident," a railway official at the accident site said.
"Most of the passengers in the derailed coaches were sleeping when the accident took place," said police officials.
Thirty trains, including 16 local ones, were affected. They were either cancelled, diverted or short terminated.
A team of senior railway officials headed by Additional General Manager B P Gupta and Divisional Railways Manager, Delhi, Ashwani Lohani along with medical team immediately rushed for the site of incident.
"After boarding the train, I fell asleep. A few hours later, all of a sudden I felt a severe jolt and fell from my berth," 58-year-old Harjinder Singh of Dholia Khurd village in Punjab's Moga district told PTI.
"I broke my right hand. When I turned around, I could see that passengers had fallen on top of one other. It was a horrific scene, but luckily, we got timely help. Ambulances reached there and we were extricated from the train," he said.