A former employee of the Indian Air Force, believed to be the mastermind behind the explosion aboard the Bhopal-Ujjain train on Tuesday, was arrested in Kanpur by the Uttar Pradesh Anti-Terrorism Squad on Thursday. Mohammed Ghaus Khan has technical knowledge and is a “hardcore member of the module”, said Additional Director General of Police (Law and Order) Daljit Chaudhary, Deccan Chronicle reported.

Khan was arrested along with another suspect, identified as Azhar. They are both part of the “Khorasan module”, which police said was behind the Bhopal train blast. With these two arrests, the police are certain that all eight members of the group, which is believed to have been influenced by the Islamic State group, have been captured, NDTV reported.

The ex-IAF employee had supplied arms and ammunition to Saifullah, the suspect in the train explosion case who was killed in an encounter in Lucknow on Wednesday. The 22-year-old’s body was found at the site of the 12-hour-long gunfight, along with arms and ammunition, mobile phones and other provisions.

Chaudhary had said on Wednesday that Saifullah might have been “self-radicalised”, and that there was no evidence to prove he had links to the so-called Islamic State group. The Uttar Pradesh Anti-Terrorism Squad had originally claimed he was a member of a local Islamic State cell.

On Tuesday, at least nine people were injured in the blast on the passenger train, three of them critically. The state had announced that it was a terror attack and promised compensation of Rs 25,000 for the injured, and Rs 50,000 for those in critical condition.