Thiruvananthapuram, April 16 : In the April 2 train fire incident in Kerala, the Kerala Police are still in dark over the motive behind the attack. The assailant, Shahrukh Saifi from New Delhi is in police custody after the Central intelligence bureau provided the tip. The Maharashtra ATS took him into custody from Ratnagiri and handed him over to the Kerala Police team. Even though Saifi has been in the state police custody for the past nine days, the Kerala Police have not been able to crack the case as he is claiming repeatedly that he was alone in the attack. Three people, including a two-year-old toddler, died by falling from the train during the burning incident. The National Investigation Agency (NIA) has already stated that this was a terror attack and that external forces were behind Shahrukh Saifi. Police have also found that he had bought two bottles of petrol for burning the train compartment. The police have also found that he had bought the petrol from a fuel pump station at Shoranur in Kerala. There are several unanswered questions as to why the assailant had reached Shoranur and whether he had received any support there. The assailant, according to police, spent around 14 hours in Shoranur is the main angle on which the investigation is centered. Shoranur is a major hub of Islamist groups and the banned Popular Front of India has a strong base in this area. Even as the PFI is banned, its political arm, the Social Democratic Party of India (SDPI) is having a presence and almost all the PFI leaders are now with the SDPI. With the Kerala Police not being able to crack the case on why Shahrukh Saifi has reached Kerala and what was the reason for burning the train, the CBI investigation seems to be a necessity, say sources. According to information available from Kerala Police sources, Shahrukh Saifi seems to have received good psychological training of not wilting under pressure. /IANS