The Uttar Pradesh Police had arrested the four men from Mathura on the night of October 5 when they were on their way to Hathras from Delhi. They are allegedly linked to the PFI and its associate outfit Campus Front of India (CFI).
The four have been identified as Atiq-ur Rehman of Muzaffarnagar, Masood Ahmed of Bahraich, Alam of Rampur and Siddique, a journalist from Kerala's Malappuram.
The UP Police also seized their mobile phones, laptops and some literature, which could have had an impact on the law and order situation.
The ED in its submission in Mathura court seeking permission for their questioning said, "Masood Ahmed has been a member of PFI and had received funds in his bank account. He was also in touch with PFI's General Secretary Mohammad Iliyas."
Their role in the riots in northeast Delhi in February this year has been suspicious and thus they need to be questioned by the financial probe agency in the Mathias jail, where they have been lodged since their arrest, the ED said in court.