A British dad and son had strangely coloured liquids in their noses when they were found poisoned, it has been reported.
Rafiqul, 50, and Mahiqul Islam, 16, were discovered dead in a rented flat in Sylhet, Bangladesh.
Three of their relatives currently remain seriously unwell and are receiving treatment at a hospital in the city, Wales Online reports.
Rafiqul's wife, 40-year-old Hosne Ara Islam, was found unconscious alongside their 20-year-old daughter Samira and son Sadiqul, 24.
Local media Prothomalo reported that an autopsy found "light blue and brown liquids in their nose" and it is hoped this may help police work out how the family was poisoned.
District Superintendent of Sylhet police Farid Uddin said the deaths "at first glance... looks like murder using poison".
He told Wales Online: "After discussing the overall situation with the doctors and inspecting the scene we believe this may have been a case of poisoning.
"The investigation is ongoing into whether it is poisoning or something else."
Police confirmed the Islam's inlaws were also living in the building and four people were questioned.
Anfor Ali, Rafiqul's father-in-law, and his wife Badrunnesa were questioned along with their son Delwar Hossain and his wife Shova Begum.
Abdul Mumin Khan, the brother-in-law of Rafiqul, told the BBC : "I didn't know what to do or what to say. Everyone is very sad. Everybody is crying. My wife, all the time, is crying. I am crying as well. I can't believe this has happened.
"This person is very friendly, a very nice guy. His son is very sweet and friendly. Everyone likes him and he likes everyone. His son is a very, very nice boy."
The family fell asleep in the same room on Monday, July 15 and weren't discovered until the next day when relatives tried to open their flat at around 10am in the morning.
A neighbour in Cardiff was shocked by the incident, saying they "are a quiet family who do their own thing".
They said: "I thought maybe it had been an accident and then we heard something about poisoning. What happened is just speculation at the moment. It's really sad.
"We've been living near them for more than 25 years. I couldn't believe it, I've been getting so many phone calls. They were just a nice, neat family. They've been away for a couple of weeks."
Tributes to taxi driver Rafiqul and his family have continued to pour in and Muhibur Islam of the Jalalia Mosque and Islamic education centre in Cardiff said there was "absolute disbelief" within the local community.
