The hired driver, who was behind the wheel instead of the regular driver, opted to cross the railway line through an unmanned railway level crossing though there are two manned railway crossings in Masayipet village, a senior officer said.
Eighteen persons, including sixteen children along with the bus driver and cleaner, were killed when Nanded-Secunderabad Passenger train collided with the bus on the railway track at around 9 AM.
The accident was so severe that the train dragged the bus, carrying 36 children, to a distance of around 50 metres before coming to a halt.
The deceased children were in the age group of 5-15 years and some of them were students of nursery class, the officer told PTI.
Medak district In-charge Collector A Sharat said that despite having manned railway-level crossings in the village, the driver took a short cut and opted to cross the railway line through an unmanned crossing.
"The driver took the unmanned gate to cross the railway track as the distance through a manned gate is a bit longer. This has proved fatal for the students. While 13 of them died on the spot, another three died on way to hospitals.
Both driver and cleaner of the bus were also killed and 22 injured children are undergoing treatment," Sharat said.
He said many of the children are in a serious condition.
A senior official of South Central Railway (SCR) said the village has three level-crossings, out of which two are manned and one unmanned, within the distance of 1.5 km.
According to a GRP officer as the regular driver of the private school bus was on leave, the vehicle was driven by a hired driver.
"Today the bus was driven by an hired driver in place of the regular driver, who had been on leave. The regular bus driver used to be alert and would watch both sides of the track while crossing the site where the accident took place," Telangana, GRP IG, Kripanand Tripathi Ujela said.
"One Bikshapati Goud, the temporary driver who was driving the bus seems to have not noticed the speeding train coming on the track, and unmanned level crossing is also another issue resulting in the mishap," Ujela, who is supervising the relief and rescue operation at the scene said.
All the bodies of children have been shifted from the spot to different hospitals and will be handed over to their parents after postmortem is conducted.
"Over 20 others who were injured in the incident have been rushed to different hospitals in Hyderabad," he said.
Meanwhile, mild tension prevailed at the spot as hundreds of villagers gathered and hurled stones at police demanding a strict action against those responsible for the incident.
"There is lot of commotion right now. The highway has been jammed due to the road-blockade and police were dispersing the crowd," another police officer said.
The accident site falls between Masaipet and Wadiaram railway stations on Secunderabad-Nizamabad section of Hyderabad division.