The source of a bug which killed a Black Country maintenance engineer remains a mystery despite a major investigation centred on his workplace.

A jury has returned an open verdict at an inquest on Paul Worrall, who died from Legionnaire’s disease on April 14, 2006. Mr Worrall, of Blake Hall Close, Brierley Hill, died a week after contracting the illness.

But the inquest at Smethwick Coroners Court yesterday heard there was no evidence to say Mr Worrall, had come into contact with the legionella bacteria at work.

Black Country coroner Robin Balmain cut the inquest short on the second day following evidence from the Health and Safety Executive’s (HSE) principal specialist inspector Dr Ian Gardner.

The case on the 44-year-old maintenance engineer at Eaton Ltd in Quarry Bank, was expected to last for four days. But Dr Gardner told the jury legionella bacteria was a naturally occurring bug found in normal water courses.

He said the bacteria could affect any hot or cold water system, adding: “It’s often very difficult to trace a case of Legionnaire’s back to a specific source.”

The inquest had heard evidence from subcontractors who were hired to clean and chlorinate the three cooling towers at Eaton’s automotive premises just two months before the father-of-one’s death.

But Mr Balmain recommended the jury returned an open verdict due to lack of evidence that the Eaton automotive factory was the source of the deadly bug.

Speaking after the verdict Mr Worrall’s widow Amanda and mother of their nine-year-old daughter said she was “shocked” at the outcome.