Kolkata/IBNS: The Central Bureau of Investigation (CBI) has ruled out gangrape in the RG Kar case, where a junior doctor was brutally raped and murdered last month and that available evidence indicates only Sanjay Roy, arrested by the Kolkata Police, was involved in the crime, NDTV quoting sources reported on Friday.

Sources told the channel that the inquiry is in its "final stages" and that the agency will soon file its charges.

The CBI was handed over the case after the Kolkata High Court expressed dissatisfaction and pointed out several lapses in the investigation by the Kolkata Police.

The central probe agency is under pressure from West Bengal Chief Minister Mamata Banerjee who, in turn, is at the receiving end from her political rivals and civil society activists over the gruesome crime.

Last week she demanded an update. "I asked for five days' (for the police to probe before she called in the federal agency) but the case was sent to the CBI. They don't want justice. They want a delay. It has been 16 days, where is justice?" she asked during an event in Kolkata.

Also read: Ex-RG Kar principal Sandip Ghosh's aide Prasoon Chatterjee, who was seen at crime scene, detained by ED in money laundering case

Banerjee's colleague, state Minister Bratya Basu, has also demanded a progress report on the case.

"Twenty-three days have passed (since the case was transferred)... there is no progress report from the CBI. We demand a detailed report of the investigation. When Kolkata Police was investigating, regular updates were given through press conferences," he said during a press conference.

Sources told NDTV that the agency has sent a medical report with DNA from the accused to experts at the government-run All India Institute of Medical Sciences in Delhi.

The agency will look to wrap up this inquiry after receiving the doctors' final opinion on the DNA sample.

As per NDTV's sources, the CBI, after recording over 100 statements and conducting 10 polygraph tests, including two of ex-hospital principal Sandip Ghosh, has no reason to believe that other people were involved in raping and murdering the 31-year-old PGT doctor, whose body was found in the seminar room of the medical facility on August 9.

The agency has made three arrests of its own, the biggest of which is Sandip Ghosh, who quit days after the killing on "moral grounds" but was appointed to head of the state-run National Medical College.

Three others were arrested too, including Ghosh's security guard.

Since his arrest, the Bengal Government and the state health body have suspended Ghosh. He had already been suspended by the Indian Medical Association.

Earlier in the day, the CBI raided Ghosh's house in Kolkata again.

The CBI is expected to file a status report with the Calcutta High Court on September 17.

Meanwhile, the Supreme Court will hear the suo moto case in the RG Kar horror on Monday.

Ahead of the hearing, the civil society has once again called for a third-night vigil on Sunday followed by an early morning protest on Monday.

Since the case came to light, Kolkata and the rest of Bengal have been witnessing massive protests by junior doctors and people from all walks of life demanding justice for the RG Kar case victim.

All inside images by IBNS team