Mahmood has been arrested and the formalities in this regard are being completed by the Barabanki police, IG, Law and Order A Satish Ganesh said.
A district court in Barabanki had yesterday issued a non-bailable warrant against Mohammad and two others in connection with the incident and fixed June 25 as the next date of hearing.
Iqbal, a former member of the state planning commission having status of state minister, and his four associates had clashed with the employees of the toll plaza on June 8, 2015 and opened fire there.
Subsequent investigations revealed that their Range Rover, which was seized by the police, did not have proper documents.
Investigations so far have revealed that SUV was registered in Haryana in the name of "whatapp son of '0' (zero)".
Superintendent of Police (SP), Abdul Hamid said the vehicle was registered in a fictitious name and the address does not exist and a team has been sent to Gurgaon for further probe.