New Delhi/IBNS: The Central Bureau of Investigation (CBI) will investigate the three-train tragedy in Odisha's Balasore, which left 275 dead and around 1,000 injured.

The move is significant considering that only a detailed probe by a top agency can establish if there has been any criminal tampering with the point machine or the electronic interlocking system, or if the train changed tracks due to reconfiguration or a signaling error.

The CBI inquiry will answer all queries regarding the accident, the worst in the country in the last two decades.

Along with the CBI inquiry, the probe by the Commissioner, Railway Safety, will also continue and a report is expected in two weeks.

On Sunday, Railway Minister Ashwini Vaishnaw said that the "root cause" of the accident and the people responsible for it have been identified.

Prime Minister Narendra Modi said a day earlier that strictest action will be taken against those found guilty.

Vaishnaw said a change in the configuration of the track may be the cause and that "whoever has done this will be not spared".

Railway experts said the electric point machine is the most important device for railway signaling, necessary for the locking of point switches, and critical for the safety of the trains.

Meanwhile, train services resumed after over 50 hours of one of the ghastliest train tragedies at Bahanaga Bazar Station in Balasore.