The room next door to where a British couple died in an Egyptian hotel last month had been fumigated with "farm-strength" insecticide just hours earlier, it has been confirmed.
John Cooper, 69, and his wife Susan, 64, died after being taken ill at a Thomas Cook Hotel in the Red Sea resort of Hurghada.
An investigation was launched after the couple died at the luxury five-star resort, although a further post mortem into their deaths will be carried out when their bodies are repatriated, Daily Mail reported.
Egyptian officials said on Monday they would release the bodies so they can be returned to the UK.
According to The Times, the day before the couple died, August 20, Namaa Agricultural and Engineering Services sprayed an adjacent room with lambda-cyhalothrin 5 per cent.
The door of the room, which was sealed with tape, was at the end of the corridor next to where the Coopers were due to stay.
It is feared the fumes may have entered their room through the ceiling space.
According to the University of Hertfordshire, the spray is highly toxic to mammals and is a known irritant.
A World Health Organisation bulletin from 1990 investigated possible poisoning cases involving the insecticide.
According to the report: "Acute pyrethroid poisoning in humans is characterised by headache, nausea and, when severe, by muscle fasciculation (spontaneous contractions) and convulsive attacks."
Their daughter Kelly Ormerod has previously said said vital clues may have been lost when cleaners and maintenance workers accessed the room soon after her parents died.
Ms Ormerod has always been adamant that she believes something in the room killed her parents, despite Egyptian officials insisting their deaths were "normal for an old English man and his wife" and the result of respiratory and heart failure.
She has previously mentioned a "funny smell" in the room at Steigenberger Aqua Magic Hotel the night before they died.
The results of the post-mortem were still pending on Friday, nearly three weeks after the tragic double death.
However confirmation has now been given by Egyptian authorities that their bodies have been released and can be taken back to the UK.
Egypt's General Prosecutor released a statement ordering the release of the bodies of Susan and John Cooper to a UK Embassy representative in Cairo.
The statement says the results of the autopsy will be released at a later stage and that the investigation will continue.
It says they can now be repatriated and the British can conduct their own post-mortem.
Ms Ormerod told ITV News that she had returned to her parents' room on Wednesday the day after their deaths to collect belongings and noticed the cleaners had been in.
"All the floors had been mopped, all the bedding had been changed and for those 24 hours maintenance were in and out quite often.
"If it happened over here it would have been taped off but the room wasn't taped off until I believe the Thursday so everybody and anybody could go in that room on that Wednesday."
She said she had "no idea" what maintenance had been doing.
Ms Ormerod believes potentially crucial evidence may have been lost in the process.
"There was obviously evidence left over from my Mum and Dad in that room which I think was quite crucial as to why they possibly died.
"There was a distinct change of smell in the room. The air conditioning unit was a lot crisper and cooler and you could tell that somebody had been in that room doing something."
Ms Ormerod had reported a strange smell in the room in the hours before they died.
She also said her daughter had intended to stay the night with her grandparents but returned to her room due to the odour.
The couple had been staying next to a room that had been fumigated just hours before, raising fears they may have been poisoned by toxic gases.
The Mail on Sunday revealed that pest controllers sprayed chemicals into the room on August 20, the day before Susan and John Cooper died.
The fumigated room – number 5106 – is located at the end of the first floor. The only connected room was that occupied by the couple.
Speaking with the BBC Ms Ormerod explained: "At 11 o' clock I went to knock on the door to see if they were just having a bit of a lie in and didn't want to be bothered, and as I opened the door I could see that my dad was extremely ill.
"He was staggering back to the bed. Mum was laid on the bed. And I could tell there was something seriously wrong with them."
Ms Ormerod said she was feeling "disheartened" that neither post-mortem results had been returned, but didn't think "the answers will be the answer I necessary believe".
Her father died in the couple's room at the hotel while Susan was later rushed to hospital where she later passed away.
Egyptian authorities ordered an investigation into the deaths despite saying the British couple died of natural causes.
Thomas Cook evacuated 300 guests staying at the all-inclusive Steigenberger Aqua Magic Hotel in the Red Sea resort town of Hurghada.
Around 200 people have lodged sickness complaints against the resort.
Thomas Cook commissioned an independent hygiene specialist and air quality specialist to conduct a series of tests at the hotel.
They said the tests on the food and hygiene standards identified a high level of E.coli and staphylococcus bacteria.
The travel firm said its experts did not think E. coli killed the Coopers.
It said the results of the tests identified "a high level of E. coli and staphylococcus bacteria", which were reviewed by Dr Vanya Gant from University College London Hospitals NHS Foundation Trust.