An apparently healthy British couple who suddenly fell ill and died at a Red Sea resort in Egypt last month may have been exposed to high levels of E. coli and staphylococcus bacteria in the food supply at their hotel, according to test results released on Wednesday by the tour operator they used to book their vacation.

But the tour company, Thomas Cook, said it did not believe that the tests, conducted by an independent hygiene specialist and air quality specialist, “shed any light on the still unexplained cause of death” of its customers, John Cooper, 69, and his wife Susan Cooper, 64, on Aug. 21.

The sudden deaths shook Egypt’s ailing tourism industry and prompted Thomas Cook, one of the best-known package tour companies in Britain, to evacuate hundreds of its customers from the Steigenberger Aqua Magic Hotel in Hurghada. The company said autopsies by the Egyptian government might determine their cause of death.

“It is clear from these results that something went wrong in August at the Steigenberger Aqua Magic Hotel in Hurghada and that standards fell below what we expect from our hotel partners,” the company said in a statement. “It is likely that the presence of E. coli and staphylococcus would explain the raised level of illness reported among guests at the hotel during this time, supporting Thomas Cook’s decision to remove our 300 customers.”