The Delhi Police questioned two men allegedly linked with three accused arrested in Bihar for a suspected terror-angle in the derailment of Patna-Indore Express in Kanpur last year.
The special cell had picked up Zia-ul Haq and Zuber were from Okhla area in south east Delhi on January 16 for questioning but no clues have been found to suggest their involvement in the derailment so far, sources said.
The National Investigation Agency (NIA) is looking into the claims of three arrested persons in Bihar that the derailment of Indore-Patna Express, in which at least 150 people were killed, was carried out at the behest of Pakistan's spy agency Inter-Services Intelligence (ISI).
The trio -- Moti Paswan, Uma Shankar and Mukesh Yadav --were arrested earlier this week by Bihar Police from East Champaran district of the state.
The Uttar Pradesh STF and Railway Police, who are investigating the terror angle in the derailement, are not "convinced" by Bihar police's claims so far, sources said.
Read | ISI role in Indore-Patna Express train mishap? NIA team to probe claims of three arrested persons
The special cell has also not been able to link either Zia or Shoaib with the three arrested in connection with the case though it was claimed that their phone numbers were saved in the mobile phone of Paswan, they claimed.
A Dubai-based Nepali citizen named Shamshul Huda had allegedly recruited Moti Paswan and others suspected to have been involved in what the police claim was a sabotage to derail Indore-Patna Express near Kanpur.
Zia-ul is a distantly related nephew of Huda, sources said. A report is said to have come from Nepal confirming the Bihar Police's claim that Pakistan's ISI had paid money to its agent Brajesh Giri for triggering blasts on railway tracks targeting trains in Bihar, they said.
Bihar police had claimed to have unearthed a suspected ISI link to target the railways with arrest of three persons in East Champaran district of the state bordering Nepal and they are being interrogated to find out if they had a role in the derailment at Kanpur Dehat in November and elsewhere. Police claimed the trio had confessed to having worked for a Nepalese contact suspected to be connected to ISI to target the railways.