CBI sources said the agency is also translating into English all the documents collected from Mumbai Police which were mainly in Marathi.
The agency, which has taken over the murder case probe, has asked Maharashtra Government to preserve samples of stomach wash, urine and blood of Indrani which were collected during her recent hospitalisation.
The agency has also asked the state government to provide it with inquiry report of Byculla women's prison authority and any other report prepared by other authorities and action taken with regard to the incident.
Indrani, who is currently in jail, was admitted to state-run J J Hospital here on October 2 in an unconscious condition after she complained of "uneasiness" and was discharged four days later.
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After Indrani's hospitalisation, conflicting reports had emerged on suspected drug overdose in prison. While one report said she had overdosed on anti-depressant pills, the other fsaid it had found no evidence of this.
Maharashtra government had ordered probe in the incident under IG (Prison) Bipin Kumar Singh.
The two other accused in the case are Shyamvar Rai, Indrani's former driver and her ex-husband Sanjeev Khanna.
The sources said DIG Lata Manoj Kumar, who is supervising the probe, has asked the team to minutely scan all documents provided by Mumbai Police, which was probing the matter, before the questioning session can begin in the prison.
CBI is trying to see if there were any loose ends in the findings of Mumbai Police which need to be probed to make it a watertight case "following which all aspects of motive which could be behind the killing will be examined", the sources said.