Pakistan cricket coach Bob Woolmer was not strangled, a UK government pathologist has concluded, according to the Times newspaper.
Mr Woolmer was found dead in his hotel in Jamaica on 18 March
Dr Nat Carey said after studying autopsy material that death was not by asphyxiation from strangling, it said.
The Jamaica Gleaner newspaper has separately cited Scotland Yard sources as saying Mr Woolmer was not murdered.
Mr Woolmer was found dead in his hotel in Jamaica after Pakistan's first-round exit from the World Cup.
The comments from the UK sources led Jamaican opposition lawmaker Derrick Smith to say the case had become a "global embarrassment" for the Caribbean nation.
There have been a number of contradictory claims about the cause of Mr Woolmer's death since his body was found on 18 March.
On Tuesday, Jamaican deputy police commissioner Mark Shields again insisted the case was being treated as a murder investigation.
The Times was citing sources close to the investigation of Dr Carey.
It said there was growing speculation that death was by natural causes, although it gave no new information on what may have led to Mr Woolmer's death.
The results of toxicology tests are still awaited but the Times said they might indicate the levels of a herbicide said to have been found in his body.
The herbicide is used for weeding cricket pitches. The tests may show whether the level was sufficient to have triggered the sickness and diarrhoea Mr Woolmer suffered before death, it said.
Heart trouble has been suggested as another cause for the death of Mr Woolmer, 58, who also suffered from diabetes.
The original autopsy said Mr Woolmer may have suffered manual strangulation, indicated by a broken bone in his neck.
UK authorities were asked to help with the investigation.
The Jamaica Gleaner said Scotland Yard's pathology report said Mr Woolmer "died of natural causes and not manual strangulation as was initially reported by Mark Shields".
The paper said the report contradicted that of the local pathologist, Dr Ere Sheshiah.
Jamaican police spokesman Karl Angell said such press reports were "unhelpful" and urged the media "to refrain from speculation because of the additional distress it places upon the Woolmer family".
Mr Shields said: "Every theory, from weed killer to aconite, has come from the media, not the police... We maintain that this is an ongoing murder investigation."
Derrick Smith, of the Jamaica Labour Party, said the case had jeopardised the reputation of the nation's police.
"The matter has become a global embarrassment for us," he said.
No-one has yet been arrested in connection with Mr Woolmer's death, which overshadowed the cricket World Cup.
Investigations have included the possibility of murder by a disgruntled fan, player or by figures concerned Mr Woolmer was going to make allegations of corruption.