Kozhikode: Police suspect the man who set his co-passenger on fire aboard an express train in Kozhikode belongs to Uttar Pradesh (UP).
Sources said the cops are considering the incident as a pre-planned attack.
They are also checking the terrorist and Maoist links with the incident.
While the anti-terrorist squad is also investigating, the Railway has also announced a probe. Forensic and fingerprint analyses have been completed.
The Union Home Ministry and the Railways have sought information from the state regarding the incident. Central investigation agencies have also probed the details. Meanwhile, K Muraleedharan, MP has issued an adjournment motion in the Parliament seeking the Central Government to investigate the matter.
The attack and the resultant fire killed three, including a woman and an infant, and injured nine other passengers.
Investigators have found a book on the railway tracks that contains notes in English and Hindi, leading cops to suspect the assailant is from UP.
There are no writings in Malayalam, sources said, and the book mostly has place names like Kazhakoottam, Chirayankeezhu and Kanyakumari.
In English, the letter 'S' is written in a bigger size, which also contains a few mathematical calculations and notes. It has many dates and names of railway stations too.
Police have found a mobile phone, glasses, purse, clothes, snacks, a pen, and a bottle of petrol in a bag they recovered on the tracks.
The incident took place around 9.45 pm on Sunday, when the Alappuzha-Kannur Executive Express train reached the Korapuzha railway bridge after crossing Kozhikode city.
The assailant poured petrol into the D1 coach and lit it on fire. Injured passengers, including three women, are under treatment at various hospitals.