John and Susan Cooper, from Burnley, Lancashire, died on Tuesday morning while on holiday at the Steigenberger Aqua Magic Hotel in Hurghada with their daughter and her three children.
An inspection of the couple’s hotel room revealed there were no toxic or harmful gas emissions or leaks, prosecutor Nabil Sadeq said.
The deaths of the couple, aged 69 and 63, prompted tour operator Thomas Cook to evacuate 301 of its customers from the hotel as a “precautionary measure”.
The travel firm’s chief executive, Peter Fankhauser, has told Sky News that the company had brought in experts to test water, food and air conditioning and the results of the tests should be known within ten days.
“We have no real evidence what caused the deaths, but what I can promise is at Thomas Cook we are doing everything to support the family and to support the Egyptian authorities… to get to the bottom of it and to get to the cause,” he said.
“There is no evidence that it is a carbon monoxide poisoning. We have no evidence but I don’t want to rule out anything before I really know the cause.”
Mr Fankhauser continued: “Twenty-four hours after the couple died we had we had our specialists… in the hotel. They took probes of the food, of the hygienic systems, of water, as well the air conditioning systems, and all those probes are now in Egypt.
“They are now examining and testing the probes and we support them in doing that, but that takes about 10 days.”
Egyptian authorities dismissed criminal motives as being behind the deaths.
Medical examinations showed that the couple both fell ill after suffering “respiratory failure” while staying at the popular hotel, Egyptian officials say.
The local governor’s office said the cause of Mr Cooper’s death was “a sudden stoppage of the heart muscles and respiratory failure”, with his wife dying due to “a stoppage of circulation and respiratory failure”.
The findings were made public shortly after daughter Kelly Ormerod revealed they had been “in perfect health” just hours before they died.
She told Sky News she was convinced that “something suspicious” had happened to them, having enjoyed a family meal and then seen them off to bed at around 1.30am.
Ms Ormerod, who found them unwell at around 11am, said: “I watched them die before my very eyes and they had exactly the same symptoms.
“I believe something suspicious has gone on. I don’t believe anyone has entered the room, but something has happened in that room that caused them to be taken away from us.”
Ms Ormerod, who is now back in the UK with her three children, told Sky News she has hired a local lawyer to find out what happened to her parents.
At least 20 people have brought legal claims against the hotel over hygiene standards.
Nick Harris, a lawyer who is representing the group, said his clients had reported becoming unwell after recent stays at the Steigenberger Aqua Magic Hotel.
Mr Harris told Sky News complaints had been made over “the food, the temperatures of the food, things like that”.
He added: “It seems to be the same complaints coming back time and time again.”