The CBI on Tuesday started its investigation into alleged criminal negligence leading to the Balasore train accident which claimed 278 lives after registering an FIR, officials said.

A team of CBI officials, along with forensic experts, which had reached Balasore district on Monday, started the probe immediately after the registration of the FIR at 2.15 PM on Tuesday, they said.

The registration of an FIR is the starting point of the CBI investigation because the agency cannot collect any document or material, question witnesses, record statement or conduct searches without it, they said.

The central probe agency was roped in by the Ministry of Railways after a preliminary inquiry flagged tampering with the electronic interlocking system, which detects the presence of trains, and officials suspected "sabotage" behind the Friday accident.

"The Central Bureau of Investigation has registered a case on the request of Ministry of Railways, consent of the Odisha government and further orders from DoPT (Govt. of India) relating to the train accident involving Coromandel Express, Yashwantpur-Howrah Express and a goods train at Bahanaga Bazar in the state of Odisha on 2nd June," the CBI spokesperson said.

The agency, which has little expertise in dealing with the functioning of railways, may need the help of rail security and forensic experts to get to the bottom of the case, the officials said.

The CBI took over the FIR registered by the GRP ( Government Railway Police) Cuttack on June 3 under IPC sections 337, 338, 304A (causing death by negligence) and 34 (common intention), and sections 153 (unlawful and negligent action endangering lives of Railway passengers), 154 and 175 (endangering lives) of the Railways Act.

The FIR stated many deaths were due to injuries caused due to the collision and electrocution after coming in contact with overhead low tension line.

The overhead wires snapped as coaches which toppled over in the triple train accident brought down electrical poles, officials said.

According to the procedure, the CBI re-registers the local police case as its own FIR and starts the probe. It can add or remove a charge from the FIR in its charge sheet filed after its investigation.

Talking to reporters in Odisha on Sunday, Railway Minister Ashwini Vaishnaw had said, "We have recommended a CBI probe into the triple train accident...."

The Railway Board Member (Operations and Business Development) wrote to the Centre on June 4 seeking a CBI probe.

The Odisha government gave its consent to the CBI to conduct investigation through a letter on Monday.

It was on Tuesday that the Department of Personnel and Training (DoPT) finally issued the mandatory notification to the CBI giving the government's go-ahead to start the investigation following which the agency swung into action and registered the FIR at 2.15 PM, documents show.

The crash involving Bengaluru-Howrah Superfast Express, Shalimar-Chennai Central Coromandel Express and a goods train occurred around 7 PM on Friday near the Bahanaga Bazar station in Balasore district.

The accident, one of the worst train tragedies in the country, claimed 278 lives and left more than 1,100 people injured.

Both passenger trains were at high speed, and experts have cited it as one of the main reasons for the high number of casualties.

-With PTI Input