Hotel staff are said to be "devastated" after two guests died in a swimming pool incident.
A man in his 30s and a woman in her 20s were found in the water at Down Hall Country House Hotel in Hatfield Heath, Essex.
Staff dived in to try to save them after they were found at about 7.35pm on Saturday, but their efforts were in vain.
Manager Chris Falcus said: "We are devastated by this tragic incident and our thoughts are with the families and friends of those concerned. As soon as the alarm was raised, two of our team dived into the pool and did everything they could to try to save them. We are co-operating fully with the police investigation."
A police spokesman said: "Hotel staff and ambulance crews tried in vain to revive the man and woman, but both were later pronounced dead at the scene." He added: "Officers from the Kent and Essex Serious Crime Directorate are investigating and are treating the deaths as unexplained at this stage."
The people are believed to be from the London area. Post-mortem examinations are expected to be carried out on Monday.
The hotel describes itself as one of England's most established country house hotels. Located near Bishop's Stortford on the Hertfordshire and Essex border, it is 45 minutes from central London and also convenient for Stansted Airport.
Dating back to 1322, the Italianate mansion offers a historic setting, with luxury interiors and ornate ceilings. There are 110 acres of surrounding woodland, parkland and landscaped gardens. The hotel was hosting weddings, birthday parties and christenings this weekend.
Chief Inspector Nick Lee told reporters at Great Dunmow police station that the people were staying at the hotel together. He said: "As part of the investigation we are trying to focus on what the relationship was between the victims."
Police were not currently looking for any other parties in connection with the incident. Asked if the people had been going to any of the functions taking place at the hotel, he said: "It's a very busy hotel, there were a number of functions going on. At the moment we haven't ascertained as to whether these individuals were part of any function or not."