Police have launched an investigation after the death of a man in the Shankill area of west Belfast.
Officers were last night at the scene of a sealed-off house in Paris Street following the death.
The man was named locally as Andy Bell, who was in his late 40s or early 50s.
Local people said ambulances and police arrived at the house in the early hours of Sunday.
The PSNI has not yet commented officially on its investigation.
However, a source said: "Initially it was thought the man was stabbed, but one theory is that he may have suffered a heart attack during an altercation.
"But the police are staying at the scene until the results of the post-mortem come back."
DUP councillor Brian Kingston said police told him the body of a man was removed from the house, between Snugville Street and Berlin Street.
He said: "I have spoken to the police. They have confirmed the body of a man was recovered from a house in Paris Street.
"They haven't told me what age, but said it wasn't an elderly man, but an adult male. They were holding the scene and are awaiting the results of a post-mortem.
"They received a phone call in the early hours of this morning, which resulted in them attending.
"In response to rumours a man was stabbed, police have told me specifically there is no indication of that currently, so they have no indication that a crime has occurred and we must await the results of a post-mortem.
"With any sudden death they will treat this as suspicious as a matter of course, but at this stage they are saying there is no indication a crime has been committed.
"They couldn't tell me if the man was from the area.
"This is a terrible tragedy for the family of this man and our thoughts are with them at this very sad time."
In Paris Street last night shocked neighbours said police were at the scene all day and a huge forensic operation had swung into action before the body was removed early in the afternoon.
One woman said: "Something seemed to happen around 1am in an upstairs flat, where a man lives alone.
"He had just moved in about three months ago and the whole area was sealed off all day.
"The police wouldn't tell local people what happened, but did say they were investigating a 'serious crime'."
Another woman said: "I heard raised voices last night and turned off my TV, but heard nothing after that.
"A couple of ambulances came to the scene, along with the police."
Another resident said: "This is a very quiet street and everybody is shocked that somebody has died suddenly."