A firefighter is thought to have taken his own life after being interviewed by detectives investigating allegations of sexual abuse within the Essex fire service dating back to the 1970s and 80s.

The man, who was in his 40s, was found dead at his home in Colchester on Monday shortly after the questioning. The death is not being treated as suspicious.

Essex police referred themselves to the Independent Police Complaints Commission because the death was "after police contact." The IPCC carried out an initial inquiry to see if there was any causal link, and decided to allow the force to carry out its own investigation.

The force confirmed on Thursday that it was mounting a criminal investigation into "historic allegations of serious criminal offences" and appealed for alleged victims to come forward. There have been no arrests.

The allegations include claims that abuse with a sexual dimension took place during initiation rites within some parts of the service, at a number of fire stations across the county.

The allegations first surfaced within the service and managers began an internal inquiry before referring the details to Essex police. Officers from the Kent and Essex serious crime directorate have interviewed some individuals, including some alleged victims.

Staff within the service are being offered counselling and a confidential helpline has been set up. Essex fire service has told its staff to co-operate fully with the investigation.

A fire service spokesman said: "These matters were alleged to have happened some time ago, but due to their serious nature and following clear legal advice managers referred the matter to Essex police. Since then the service has been co-operating fully with the police inquiry and has advised staff to do the same. While this investigation continues it would be inappropriate for us to comment further."

Since the Jimmy Savile revelations, experts working with adult victims of sexual abuse across the country have seen a huge increase in the reporting of historic offences.

Pete Saunders, of the National Association for People Abused in Childhood, said his service's helpline was taking more calls than ever before. "People are feeling much more confident about coming forward," he said.

Essex police said in a statement: "We would not wish to comment further at this sensitive stage of the investigation. If anyone has any information which they feel may assist the police they are asked to contact the major crime team on 01279 621802."