A couple who died at a five-star hotel in Egypt were in “perfect health” before their holiday and, despite widespread speculation, no cause of death has been definitively established, their daughter has said.

Kelly Ormerod was staying at the Steigenberger Aqua Magic hotel in the Red Sea resort of Hurghada with her parents, John and Susan Cooper, and her three children, when her parents died within hours of each other.

Amid reports of a raised level of illness among guests, Thomas Cook was evacuating more than 300 guests from the hotel on Friday. Holidaymakers were offered alternative hotels in Hurghada, or the option to return home.

John, 69, from Burnley, died in his room, before Susan, 63, a Thomas Cook employee, died in an ambulance en route to hospital, Ormerod said.

She told Sky News she believed “something suspicious” had happened in their hotel room that “caused them to be taken away from us”.

“They had no illness, no stomach upset, no vomiting, no illness whatsoever – they were in perfect health when they went to bed,” she said.

“It was about 11am when I went to the bedroom. They said they were extremely ill and needed help. I watched them die before my very eyes and they had exactly the same symptoms.

“I believe something suspicious has gone on … something has happened in that room and caused them to be taken away from us.”

In a statement to the Lancashire radio station 2BRshe said the family were in “utter shock” as they awaited the results from postmortem examinations on the couple.

“As a family, we are devastated. Mum and Dad meant the world to me and the children, and we are in utter shock over what has happened and what is happening,” she said.

“Prior to going on holiday, Mum and Dad were fit and healthy. They had no health problems at all. What I want is to clear up some of what is being reported. We have no cause of death; a postmortem is under way.”

Other holidaymakers said they felt ill, and were disappointed with the level of communication from Thomas Cook and the hotel.

Alison Cope, from Birmingham, said five of her seven family members had been ill for about 10 days during their fortnight at the hotel.

“The food is just disgusting, it’s undercooked. I know so many people have been ill,” said Cope, who flies home on Friday evening. “Half the time we don’t know what it is and can’t eat it because it’s raw in the middle.”

Egypt’s tourism ministry issued a statement on Friday offering its condolences to the Coopers’ family and said the couple “died of natural causes, with no suspicion of criminal activity”, according to the preliminary medical report by the Red Sea governorate.

The ministry said James died in his hotel room at 11am on Tuesday after suffering a “sharp drop in blood pressure which had caused his heart to stop abruptly”, a medical examination found.

“At 4pm, his wife Susan Cooper was transferred to al-Assil hospital after fainting,” the ministry said, outlining how, before she died, she received treatment for 10 minutes to try to restart her heart.

A Thomas Cook spokesman said: “We are deeply saddened by the tragic deaths of two of our customers.

“The circumstances of their deaths remain unclear. We are aware of the speculation in some of today’s media that their deaths may have been caused by carbon monoxide poisoning. Currently we have no evidence to support this.”

The hotel was last audited by Thomas Cook in July and received an overall score of 96%. The listing for the hotel on the Thomas Cook website includes a line saying: “Sorry, there is currently no availability.”

However, the hotel – which can accommodate about 2,500 guests and is part of a well-respected German chain – is still taking bookings, and it was only Thomas Cook customers who were leaving the complex.

Additional reporting: Ruth Michaelson in Cairo