Five railway employees, including the station master of Bahanaga Bazar, are being investigated in connection with the three-train accident in Odisha's Balasore district that claimed 288 lives, official sources said on Monday.

The four other employees perform signalling-related job and were on duty at the time of the accident earlier this month, they said.

The sources said the five employees are discharging their duties at present and any future action would depend on the accident probe report prepared by the Commissioner of Railway Safety (CRS).

The Central Bureau of Investigation (CBI) is conducting a separate probe into alleged criminal negligence leading to the accident at Bahanaga Bazar station on June 2.

Railway Ministry officials have indicated a possible manual tampering of the interlocking system which turned the signal for the Coromandel Express to green and guided it to the loop line where it collided with a stationary goods train.

An interference with the interlocking system, which is an automated signalling system, is being seen as the major cause of the incident.

"Five railway personnel are currently at the centre of the probe. A final report from the CRS is expected soon," a senior rail official, who did not wish to be named, said.

Three possible scenarios are being probed -- whether the tampering of the system was intentional or by mistake or a consequence of maintenance work underway in the area -- the sources said.

Meanwhile, two rail workers' unions have come out in support of the national transporter amidst harsh criticism from the Opposition parties over the accident in which more than 1,000 people were injured.

In a joint statement, the general secretaries of the All India Railwaymen' Federation (AIRF) and the National Federation of Indian Railwaymen (NFIR) said that they were "anguished" how the train tragedy has been "politicised".

"We are deeply anguished to see how this train tragedy has been politicised and attacks are being launched in social media and print media on railways' performance. Each such attack is an affront to our sincerity and dedication to duty.

"Small amounts spent on ensuring safe conditions for frontline staff like loco pilots and track maintainers are being described as frivolous expenditure," they said.

They have also said that the accusations reflect the "complete ignorance" of the people about the working condition of Railway personnel.

"Whether it is the track man who patrols the track day and night, facing inclement weather or hangs from bridge girders for repairs, or the loco pilot who maintains a steadfast vigil for more than 10 hours and more, eyes glued to the track and signals, almost stationary in a small loco cabin, or the points persons who assiduously monitor yard operations...each puts himself at peril in his line of duty," the joint statement read.

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