Bassi said the SIT has finalised an "action plan" to investigate the case and did not rule out questioning Tharoor soon, saying "whatever necessary will be done" to solve the case.
"When we file a case under Sec 302 of IPC, it means we have prima facie reasons to believe that it is a case of murder," Bassi told reporters on being asked whether police have any evidence that it was a case of murder.
"We have formed an SIT to probe the case. The SIT has formed an action plan to go about the case and everything will be done as per it," he said.
Delhi Police had yesterday registered a murder case into Sunanda's death under section 302 of the IPC on the basis of an AIIMS medical report that concluded that her death was unnatural and due to poisoning, but nobody has been named as a suspect as yet. The FIR was filed against unknown persons.
Sources said the SIT is likely to question Tharoor, his relatives and personal staff along with the employees of the five-star hotel where she was found dead on January 17 last year.