Detectives are investigating the sudden death of a 62-year-old man at a factory in Salford on Thursday 28 October 2004.
The man, who worked as a security guard at Hercules Ltd on Langley Road in Agecroft, has been named as Thomas GILLIGAN of Lawlor Avenue in Salford.
He was on duty when an alarm was activated in the grounds and he saw two men, armed with machetes, enter one of the buildings in the industrial complex.
He alerted the police and locked himself in the security lodge. Officers arrived at the scene at 8.50pm and Mr Gilligan reported what he had seen. The officers were conducting a search of the grounds when they saw Mr Gilligan had collapsed.
An ambulance was called and he was taken to Hope Hospital where he was pronounced dead at 9.55pm. A post mortem will be carried out today.
Both of the offenders were wearing black balaclavas. One of them is described as being approximately 5ft 8in tall and was wearing a puffa style jacket.
Detective Inspector Bob KELLY at Salford CID said: "We are taking this burglary and the sudden death of Mr Gilligan very seriously.
"I would appeal to anyone who has any information, however small, to contact Salford CID on 0161 856 5040 or Crimestoppers anonymously on 0800 555 111."