Police have named a man who died from a single stab wound at a flat in Clayton-le-Moors as James Christopher Todd.
The 27-year-old’s badly decomposed body was found by officers at 12.15pm on Monday after neighbours reported an unpleasant smell coming from a block of flats on Rutland Close.
A post mortem examination revealed the cause of death to be a single stab wound to the heart.
Police say the stab wound was the only injury on the body.
A 25-year-old man from Blackburn has been arrested on suspicion of murder and continues to be held by detectives.
A murder investigation is now underway and a dedicated team of police officers and staff are working to establish the circumstances surrounding the incident.
The man leading the investigation, Detective Superintendent Neil Hunter from the Force’s major investigation team, said Mr Todd’s body had been there for a significant period of time.
He said: "We are looking at the relationships, associates and colleagues of the victim and the man under arrest to try and build up a picture.
"The last seven days before this man died are the gaps we need to fill. A knife caused the injury.
"It has not been recovered and we are still searching the area for it."
He added: "I would appeal to anyone with any information who could assist us with this investigation to contact us as a matter of urgency.
"I would also appeal to anyone who knew James, friends or associates who saw him recently, to get in touch as it is vital that we build up a picture of his movements in the last few days of his life.
"James’s family are naturally devastated by their loss and we have dedicated family liaison officers supporting them at this difficult time."
The discovery has stunned neighbours of Mr Todd, who say the area is usually very quiet and peaceful.
A resident said: "They cordoned off the whole block and moved the residents who live in the block out.
"It’s so terribly sad. It is someone’s son and he has got a family.
"It’s shocking to think he had been there all this time."
Local postman Peter Entwistle, 45, noticed a smell coming from the flat block on Rutland Close one week ago.
A Rutland Close resident said: "You wouldn’t expect this around here. It’s quiet. There is the odd party but never any trouble.
"It is quite scary that something has gone on like this.
"But we don’t know what is happening. It’s a big shock."