The teams of crime branch and forensic department reached the residence of Shekhar in the national capital for investigation, they said. The officials questioned Shekhar's family members including his wife Apoorva, sources added.
The autopsy report of Shekhar suggested he died of "asphyxia" as he was strangulated and smothered, PTI reported.
The autopsy was conducted by a medical board comprising five senior doctors of the All India Institute of Medical Sciences (AIIMS). "The medical board unanimously concluded that the cause of death in this case is asphyxia as a result of strangulation and smothering. It is a sudden unnatural death, placed in the category of homicide," the head of the AIIMS' forensic department, Dr Sudhir Gupta, said.
Also, IANS quoted a police officer as saying that Shekhar died an "unnatural death".
"The autopsy report of Rohit Shekhar Tiwari, 40, suggested that it is an unnatural death due to smothering. Other contradictions were also found," Deputy Commissioner of Police Vijay Kumar told IANS. "Now the case has been transferred to the Crime Branch," he said.
Shekhar, a resident of Defence Colony in south Delhi, was brought to Max Hospital in Saket area around 5pm on Tuesday, where doctors declared him dead.
According to police, Rohit's mother Ujjwala Tiwari was in Max Hospital for her treatment, when she received a phone call from home that he was unwell and bleeding from the nose. "A ambulance call was made to the hospital. Ujjwala reached her residence along with the ambulance that brought Rohit to hospital," DCP (South) Vijay Kumar said.
According to an official statement from Max Healthcare, "Max Hospital received an emergency call from the residence of Rohit Shekhar Tiwari at 4.41 p.m. An ambulance brought Tiwari to Max Hospital in Saket, where he was declared brought dead at the hospital emergency."
Rohit Tiwari joined the BJP ahead of the 2017 Uttarakhand assembly polls and recently indicated he could join the Congress. Born out of wedlock, Rohit fought a six-year-long paternity battle with his late father, after he refused to accept him as his biological son.
On April 24, 2014, the Delhi High Court, declared Rohit Tiwari's biological son. While passing the order, the court took into note the report of Tiwari's DNA test, which proved that Rohit was indeed his son.
Tiwari later married Ujjwala in Lucknow. He died at the age of 93 on October 18, his birthday, last year. The Congress veteran, who had served in various positions at the Centre, was the chief of minister of Uttarakhand and Uttar Pradesh.