The chargesheet, in which the agency will list the accused and outline the evidence against them, is to be filed in the Gujarat High Court by July 4. Sources say the CBI wants more time to investigate Mr Kumar's alleged role. He retires in a few weeks from the Intelligence Bureau.
In 2004, 19-year-old Ishrat, a college student from Mumbai, and three others were killed by the Crime Branch of Ahmedabad on the outskirts of the city. The police claimed they had been told by the state's Intelligence Bureau that the group was headed to assassinate Chief Minister Narendra Modi on behalf of the Lashkar-e-Taiba (LeT).
At the time, Mr Kumar was Joint Director with the Intelligence Bureau in Gujarat.
His interrogation and the CBI's plans to arrest him had turned into a huge point of tension between the investigating agency and the Intelligence Bureau, where M Kumar is currently Special Director.
The Ministry of Home Affairs intervened, and allegedly told the CBI that it did not have evidence to back the charges of murder and conspiracy it sought against Mr Kumar.