The National Investigation Agency (NIA) has sent a five member team to probe the derailment of the Hirakhand Express on Monday at Kuneru in Vizianagaram district.
So far 39 people have died in the accident with over 50 persons injured.
The accident will be probed by both NIA and CID. The top-rung officers of the Andhra Pradesh police will accompany the NIA team.
Could it be ISI or Maoists?
The police have recently arrested three people who allegedly confessed to taking directions from the Pakistan's spy agency, Inter-Services Intelligence (ISI), to derail the train. The three suspects are said to be behind the accident of Indore-Patna Express in Kanpur in December 2016 that injured over 40 people.
The arrested suspects had also planted a bomb that failed to explode on a railway track in Ghorasahan in East Champaran district, Bihar. They were given Rs 3 lakh to plant an Improvised Explosive Device (IED), the police said.
Apart from the ISI, the Maoists, who have been waging a four-decade-long war against the state governments in eastern and central India, have used bombs to derail trains in the past, making the group equally a suspect.
Further, the linemen had inspected the track between 9 pm and 10:45 pm on the fateful night. The particular derailment happened around 11.20 pm, suggesting the possibility of sabotage, the New Indian Express reported.
The story so far
Investigators have inspected the tracks at Kuneru railway station and the portion of 10 to 15 inch broken tracks.
With the NIA team probing the sabotage angle- which has not been ruled out by the railway officials- the possibility of the derailment due to the weakening of tracks is also being considered.
The probe team will later go to Kuneru station to collect evidence.
Investigators will also be looking into many inspects including the driver's fallibility and faulty tracks.
Are the train lines restored?
Railway officials claimed that the services in the Rayagada-Vizianagaram section of Waltair division have been restored by Tuesday morning.
However, the line where the mishap took place is being repaired and railway officials are restoring the electric traction system currently. Train operators have been advised to slow down while passing this particular stretch, the Indian Express reported.
Headless bodies recovered
Rescue workers have found at least 10 headless bodies from the ruins.
Initially, the photos of the headless bodies were uploaded at the helpdesk of the website, but was later removed fearing backlash.
One volunteer for the Red Cross said he was shocked to see some of the bodies as they were severely mangled, Deccan Chronicle reported.
Railway Minister Suresh Prabhu had announced a compensation of Rs 2 lakh each to the deceased person's families and Rs 50,000 for the injured. Additionally, Andhra Pradesh Chief Minister Chandrababu Naidu has also announced Rs 5 lakh compensation for the families of the deceased from his state.