The British couple who died in an Egypt hotel noticed a “musty smell” had filled their room in the hours before they died, an inquest heard.
At a brief hearing at Preston Coroner’s Court on Tuesday, senior coroner James Adeley revealed he would be requesting all relevant reports and documents from Thomas Cook and authorities in Egypt.
But he warned that requests to foreign countries "can take months, even years".
A post-mortem into John and Susan Cooper's deaths at the Steigenberger Aqua Magic Hotel in the Red Sea resort of Hurghada this week proved "inconclusive".
It comes after examinations carried out by authorities in Egypt reported the cause of deaths as being linked to E.coli bacteria.
Dr Adeley said neither of the couple were known to have any serious medical conditions before they left the UK for the holiday on August 13.
They were staying in one room with their 12-year-old granddaughter, Molly, while their daughter Kelly Ormerod stayed in another room with her two other children.
On the evening of August 20 the couple dined at the hotel buffet and it was thought they both ate liver before Mrs Cooper and Molly returned first to their room, 5107.
The coroner continued: "They noticed an acetone type smell replaced by what is described by the granddaughter as a funny, musty smell. A different smell from earlier in the week.
"It was established the next door room had been fumigated."
Around 1.15am Molly said the smell was making her feel unwell, Mrs Cooper called her daughter and Mr Cooper walked the girl to her mother's room before returning to his own room.
Dr Adeley continued: "On the morning of Tuesday 21st August, Ms Ormerod become concerned because neither had appeared by 11am."
Det Inspector Leah Rice, of Lancashire Police, told the hearing: "The normal routine was Susan Cooper would usually be up six, six thirty, down to the pool to reserve sun beds for the day, then breakfast.
"However that morning she was not down for the sun beds."
The court heard Ms Ormerod called for help when her father answered the door to their room and two doctors arrived.
Dr Adeley said: "Shortly after this Mr Cooper collapsed in the room and could not be revived and verified to have died at noon. Mrs Cooper was variably lucid."
The couple had been vomiting and feeling lethargic and Mrs Cooper had a heart attack in an ambulance on the way to hospital where her death was confirmed.
Dr Adeley said he had only a single document from the authorities in Egypt stating E.coli as a cause of death for the couple and explaining the strange smell in the room as a leak of pesticides from the adjacent, fumigated room.
He said he had no reports detailing toxicology, micro-biology, police or public health investigations.
Ms Ormerod, 40, said she was preparing for the funerals on Wednesday of John and Susan Cooper, in their home town of Burnley.
Outside court Ms Ormerod said: "All I would like to say is thank you very much for all the support I have received.
"At the moment now I have got to go home and prepare for a funeral tomorrow.
"If you would kindly leave me be, leave my family be, and let us grieve and get the grieving process on the way, and I am prepared to speak at a later date."
The funerals will be held in Burnley on Wednesday morning.