Rajan, 61, was lodged in the high-security Tihar Jail in New Delhi since his arrest after deportation from Bali, Indonesia, in 2015.
All the criminal cases pending against him in Mumbai were transferred to the CBI and a special court was constituted to try them.
On Monday, an assistant jailor of the Tihar jail informed the sessions court here that they could not produce Rajan via video conference before the judge for the hearing of a case as the gangster has tested positive for Covid-19 and admitted to the AIIMS.
Rajan is facing as many as 70 criminal cases pertaining to extortion and murder in Mumbai.
In 2018, Rajan was convicted and sentenced to life imprisonment in the 2011 murder case of journalist Jyotirmoy Dey.
Last week, the special CBI court in Mumbai acquitted Rajan and his aide in connection with the murder of Hanif Kadawala, an accused in the 1993 Mumbai serial bomb blasts case.