Police said they are scanning through the CCTV footage of the third floor lobby of the hotel and call records of Sunanda to ferret out details of those who she may have spoken to try and break the mystery.
The minister's personal staff and the hotel staff will also be questioned to piece together evidence and to have an idea about the state of mind she was in on the crucial day and hours before the death.
Investigators said the couple had reportedly altercations in the past and even on Thursday night they had a heated spat which continued till around 4:30 on Friday morning.
After that Tharoor had slept on a sofa in the drawing room while Sunanda was in the bed room in the suite.
Investigators said that they will summon those people with whom she spoke over phone and record their statements to understand her state of mind.
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