The south district unit of the Delhi Police, which is currently investigating the case, has already requested CFSL to expedite the viscera tests in the case which would establish the nature of the poison which led to her death.
According to a senior police official, the toxicology report from CFSL will shed light on what caused the death.
On January 21, a sub-divisional magistrate had directed Delhi Police to investigate the murder or suicide angle in the case after autopsy report has cited the death as "sudden and unnatural" while the cause of death was mentioned as poisoning.
However, the nature of the poison and the quantity can only be established after viscera tests at CFSL.
Sunanda, 52, was found dead in a 5-star hotel in South Delhi on the night of January 17, a day after her twitter spat with Pakistani journalist Mehr Tarar over an alleged affair with Tharoor.