UK post-mortems of a British couple who died while on holiday in Egypt are to start three weeks after their deaths.

However, the investigation into what killed John and Susan Cooper could take months, a senior coroner has warned.

The couple from Burnley died suddenly after being found seriously ill in their hotel room in Hurghada on August 21.

Their bodies have been brought back to the UK, where a coroner is due to open inquests into their deaths.

A Home Office pathologist will examine the bodies to indicate a cause of death.

Dr James Adeley, senior coroner for Lancashire, told Sky News: “In view of the concerns raised by this case, analysis and evaluation of the findings at post-mortem and the associated samples may take some weeks or possibly several months to analyse.

“These results will need to be compared with the findings from the Egyptian investigation, when these are available to the Home Office pathologist and the coroner.”

Egypt’s chief prosecutor said the couple had probably died from E.coli poisoning – a conclusion disputed by their daughter Kelly Ormerod, who was also on the Thomas Cook holiday with them at the Steigenberger Aqua Magic hotel in the Rea Sea resort.

Prosecutor Nabil Sadek said Mr Cooper, 69, suffered acute intestinal dysentery caused by E.coli, and Mrs Cooper, 63, a Thomas Cook travel agent, suffered a complication linked to infection, likely to have been caused by E.coli.

Sadek previously said an inspection of the couple’s hotel room found no toxic or harmful gas emissions or leaks.

There was also no evidence of criminal involvement in their deaths and tests on air and water at the hotel found nothing unusual, he added.

Thomas Cook commissioned specialists to examine the hotel following the deaths, with tests showing normal carbon monoxide levels near the couple’s room and normal levels of chlorine in the swimming pool.

However, tests on the food and hygiene standards “identified a high level of E.coli and staphylococcus bacteria”, the operator said.

The company said the independent specialists it commissioned to carry out the tests – and Dr Vanya Gant from University College London Hospitals NHS Foundation Trust – did not believe the results “shed any light” on the cause of the Coopers’ deaths.

Thomas Cook evacuated 300 holidaymakers from the hotel as a precaution 24 hours after the deaths.

Egypt’s tourism minister Dr Rania Al-Mashat said the health and safety of tourists to Egypt was “paramount”.

“We will review the attorney general’s autopsy reports in fine detail to determine our next course of action to look after the welfare of our visitors,” she said.

A spokeswoman for Steigenberger Aqua Magic Hotel, said: “We understand the Public Prosecutor’s report states that E.coli bacteria was responsible for the tragic death of Mr Cooper and is also likely to have caused the tragic death of Mrs Cooper.

“We will continue to work closely with the Egyptian authorities and experts to establish how this could have happened, given that there are a number of independent reports that have raised the issue of where and how the E.coli could have been ingested.

“We have the utmost sympathy for the Cooper family and will do everything we can to assist in any further ongoing investigations and in the forthcoming inquest.”