A British couple who died on holiday in Egypt suffered heart and respiratory failure, local authorities have said.
John Cooper, 69, and his wife Susan, 63, from Burnley, were staying at the Steigenberger Aqua Magic in the Red Sea resort of Hurghada.
The couple's daughter, who was also staying at the hotel, said she believed their deaths were suspicious.
The Red Sea governorate said medical checks by a health inspector revealed "no criminal suspicions".
Thomas Cook said it was removing all its customers from the Steigenberger Aqua Magic as a "precautionary measure". It added that the circumstances of the deaths were "unclear".
The couple's daughter Kelly Ormerod, who was staying in the hotel with her three children, told Sky News: "I believe something suspicious has gone on.
"I don't believe anybody has entered the room but something has happened in that room for them both to be taken away from me."
Mrs Ormerod said she had eaten dinner with her parents on Monday night and they were in "good health and great spirits".
She said she found them "extremely ill" the following morning and her father died in the room before her mother was taken to hospital, but could not be revived.
"I watched them die before my very eyes and they had exactly the same symptoms," added Mrs Omrerod.
In a statement, authorities in Egypt said Mr Cooper died in his hotel room at 11:00 local time on Tuesday.
He had suffered a "sharp drop in blood circulation and a sudden stop in the heart muscle", and his cause of death was listed as "sudden failure in the heart muscle and respiratory failure".
Mrs Cooper was taken to hospital five hours later in a "state of fainting" and, although heart recovery work took place for 30 minutes, she died at 17:12.
The authorities said her cause of death was a "drop of blood circulation and respiratory functions".
Thomas Cook said the circumstances of the deaths were "unclear", but it had no evidence that carbon monoxide was a cause.
It said 301 holidaymakers would have options for different hotels from Friday and those wishing to go home would be flown back.
Sven Hirschler, senior director of corporate communications for Deutsche Hospitality, which owns the Steigenberger brand, said there was not an unusual level of illness among the 1,600 guests staying at the hotel.
He said that Mr Cooper had complained of low blood pressure and was treated by the hotel's on-site doctor on the day he died.
Janette Rawlingson, 43, from Chelmsford, Essex, who arrived at the hotel with her husband and two children on Tuesday, said Thomas Cook staff told guests at a meeting it was testing samples from the restaurant and swimming pool.
"Other guests are saying there are 40 people ill at the hotel with vomiting and diarrhoea," she said.
"A reasonable person can't help but wonder if there's a link between that illness and these deaths."
Other holidaymakers have told the BBC about their experiences with illness during stays at the Steigenberger Aqua Magic.
'Tired and exhausted'
Janine Traviss, from Oldham, said she and her partner fell ill with a stomach bug during a holiday earlier this month.
"I subsequently have been ill for several weeks now since returning and had to visit the doctor on two occasions with two full weeks of antibiotics," she said.
"I am still recovering and still feel very tired and exhausted most days."
Thomas Cook said it was working closely with the hotel and supporting the local authorities with their investigations.
It stated the hotel was last audited late last month and received an overall score of 96%.
"We will be contacting those customers due to travel to the Steigenberger Aqua Magic Hotel in Hurghada in the next four weeks to offer alternative holiday options," the tour operator added.
Mrs Cooper worked at the travel firm's Burnley branch, which was closed on Thursday.
She has been described as a "loyal and long-serving" member of staff by the company.
Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways:
- WhatsApp: +44 7555 173285
- Or Upload your pictures/video here
- Tweet: @BBC_HaveYourSay
- Send an SMS or MMS to 61124 (UK) or +44 7624 800 100 (international)