Two British holidaymakers have died from Legionnaires' disease shortly after staying at a Bulgarian hotel promoted by tour operator Jet2.
Brian Taylor, 75, and John Cowan, 43, were diagnosed with the severe form of pneumonia after visiting the Hotel Kalofer earlier this year.
Investigations were launched by Jet2 and lawyers acting for the victims' families after they were killed by the virus within weeks of returning to the UK.
Jet2 says that specialist tests on water samples from Hotel Kalofer have since come back negative for Legionella, the bacteria that causes the disease.
It has transferred all customers away from the hotel as a "precautionary measure" and says it will not sell any holidays there for the rest of this year and 2020.
Mr Taylor, from Huddersfield, was admitted to hospital with flu-like symptoms days after he returned from a week-long stay in Bulgaria on June 17.
He was diagnosed with a collapsed lung, sepsis and Legionnaires' disease before he died in hospital a month later.
His family has instructed solicitors Irwin Mitchell to investigate whether his illness was linked to his stay at Hotel Kalofer.
Mr Taylor's stepson Martin Farrell, of Chesterfield, said: “When he collapsed and was admitted to hospital we couldn’t believe it.
"He had to be sedated and it was awful to see him like that in the intensive care unit.
“We thought he was turning a corner at one point but then the unimaginable happened. It was a complete shock to us all.”
Mr Cowan, from Lanarkshire, Scotland, was admitted to hospital in Clydebank, West Dunbartonshire, after falling ill while holidaying with a friend from June 4 to 11.
His condition deteriorated rapidly, and his family decided to switch off his life support after he suffered catastrophic brain damage.
The cause of his death on June 19 was given as septic shock and Legionella pneumonia.
After Mr Cowan's family announced they are suing Jet2 over his death, his younger brother Barry, 41, said: "We just want answers - to know why this happened, to know it will never happen to anyone else."
On Wednesday it emerged that a third man, who does not want to be identified, was also diagnosed with Legionnaires' disease after staying at the hotel on a Jet2 holiday in June.
He had to be put in an induced coma in intensive care after returning to the UK, but has since partly recovered and been discharged from hospital.
Legionnaire's disease is spread by bacteria in droplets of water small enough for people to breathe in.
The bacteria can grow and multiply in a building's showers, toilets and air conditioning units if it is allowed to get into the water system. Jet2 describes Hotel Kalofer as "perfect if you're looking for a relaxing getaway in the Bulgarian sun" on its website.
A quarter of the 168 TripAdvisor reviews rate it as "poor" or "terrible", with one customer claiming it was "filthy" and "never cleaned" in July.
More than half of the reviews rate the hotel as "excellent" or "very good".
Jet2 said: “Sadly, we can confirm that two customers recently passed away shortly after returning to the UK from holiday in Bulgaria.
"We would like to offer our heartfelt condolences to their families at this very difficult time, and we have been in constant contact to offer all the assistance and support that we can.
“The health and safety of our customers is our absolute priority.
"In response, and to support our investigation, two independent specialists were instructed to take samples from the hotel and a UKAS accredited laboratory conducted testing of the water samples for any contamination. "The results of all their tests were negative.
"We will continue to assist the local authorities in their investigations as required.
“Despite these results we have taken further precautionary measures, like other UK tour operators at the hotel.
"We have transferred all customers and all bookings for this summer to other hotels, and we have also put a stop on sales to the affected hotel for Summer 19 and Summer 20.”