The railways on Sunday virtually ruled out driver error and system malfunction, indicating a possible "sabotage" and tampering of the electronic interlocking system behind the triple train accident that claimed at least 288 lives in Odisha.

Railway Minister Ashwini Vaishnaw said the "root cause" of the accident and the "criminals" responsible for it have been identified.

"It happened due to a change made in the electronic interlocking and point machine," he told reporters at the site of the accident in Balasore district.

Here in Delhi, top railway officials explained how the point machine and the interlocking system function.

They said the system is "error proof" and "fail safe" but did not rule out the possibility of outside intervention.

"It is called a fail safe system, so it means that even if it fails, all the signals will turn red and all train operations will stop. Now, as the minister said there was a problem with the signalling system. It could be that someone has done some digging without seeing the cables. Running of any machine is prone to failures," Jaya Verma Sinha, Member of Operation and Business Development, Railway Board, said.

A senior railway official who did not want to be identified said this kind of tinkering with the "logic" of the AI-based electronic interlocking system can only be "intentional" and ruled out any malfunction in the system.

The minister also said that the Commissioner of Railway Safety has completed an investigation and the report is awaited.

"It could be a case of tampering or sabotage from within or from outside. We have not ruled anything out," he said.

The crash involving Bengaluru-Howrah Superfast Express and Shalimar-Chennai Central Coromandel Express and a goods train occurred around 7 PM on Friday near the Bahanaga Bazar station in Balasore, about 250 km south of Kolkata and 170 km north of Bhubaneswar.

At least 288 people were killed and around 1,175 injured in the accident.

Officials on Sunday also gave the driver of the Coromandel Express (Coromandel Express) a clean chit by stating that he had the green signal to move forward and he was "not over-speeding".

A preliminary report from the ground accessed by PTI on Friday stated that the Coromandel Express had entered the loop line at the station on which an iron ore-laden goods train was parked.

It also indicated that a tampering could have occurred stating that the signal was "given and taken off for the up main line for train number 12841 (Coromandel Express), the train entered the loop line, dashed the goods train and derailed. In the meantime, train number 12864 passed through the down main line and two of its coaches derailed and capsized." Explaining how the two components mentioned by the minister are key to train operations, Sandeep Mathur, Principal Executive Director of Signalling, Railway Board, said that these two work in coordination to show the driver whether the track is clear to move forward.

"Signal is interlocked in such a manner that it will show if the line ahead is occupied or not. It will also be known whether the point is taking a train straight or towards loop line.

"When the point shows straight and the track ahead is not occupied then the signal is green and if the point is taking the train on loop and track is clear then signal is yellow and the route is shown of a different direction," he said.

He said that the interlocking system is a safe way to guide a train out of a station.

A point machine is a vital device for railway signalling for quick operation and locking of point switches and plays an important role in the safe running of trains. Failure of these machines severely affects train movement.

Sinha said that the direction, route and signal were set for the Coromandel Express.

"Green signal means that in every way the driver knows that his path ahead is clear and he can go forward with his permitted maximum speed. The permitted speed at this section was 130 kmph and he was running his train at 128 kmph which we have confirmed from loco logs," she said.

The Bengaluru-Howrah Superfast Express train was running at a speed of 126 kmph.

"In both the trains there was no question of over-speeding. Preliminary finding has found that there is a signalling issue," she said.

"Only one train was involved in the accident, it was the Coromandel Express. The Coromandel Express crashed with the goods train and its coaches went on top of the goods train. It was an iron ore train, a heavy train, therefore entire impact of the collision was on the train," she said.

It was a fraction of a second that last two coaches of the Bengaluru-Howrah train crashed with the coaches of the Coromandel Express, she said.

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