Egypt's tourism minister said on Thursday authorities would test food and hygiene at a hotel where a British couple stayed before dying last week, and that a forensic team would complete their postmortem in the coming days.
The couple, John and Susan Cooper, died within hours of each other in the Egyptian Red Sea resort of Hurghada on August 21.
John Cooper, 69, died at the Steigenberger Aqua Magic Hotel and Susan Cooper, 63, died at a nearby hospital, prompting an evacuation of Thomas Cook customers.
No one was immediately available to comment from the hotel, which said last week there had not been a rise in cases of illness. Egypt's public prosecutor said on Saturday that engineers had checked the hotel's air conditioning system and found it to be sound.
Local officials initially said both had died from heart failure, but Egypt's public prosecutor said the cause of death was not immediately clear.
"Autopsies on the two bodies are currently being conducted by a team of forensic pathologists ... I anticipate this will be concluded during next week," Tourism Minister Rania al-Mashat said in a statement.
A team led by Egypt's public prosecutor was examining the hygiene at the hotel, testing food, water and air conditioning systems, Mashat said.
Thomas Cook CEO Peter Fankhauser travelled to Cairo to meet Mashat and Egyptian Prime Minister Mustafa Madbouly on Wednesday "to get to the bottom of what went wrong", a statement from the company said.
Egypt relies heavily on tourism revenues, which have increased this year after the industry was hit hard by the turmoil that followed a 2011 popular uprising.
Tourism revenue jumped 77% in the first half of 2018 to around $4.8bn compared with the same period last year, an official told Reuters on Wednesday.