Doctor John Osman led the research

The HSE agreed to undertake the study following claims by a group of women workers that cancer illnesses were linked with their work at the Greenock factory.

It contacted former and current employees and asked them for access to personal records.

The aim has been to establish the number of cancer cases occurring in the workforce since the plant opened in 1970.

Higher than expected levels of four cancers (lung, stomach and breast cancers in female employees, and brain cancers in males) were uncovered by the researchers.

Dr Osman said: "We now need to do more research to find out what the causes may be and establish whether there is a link with the Greenock plant.

'Internal factors'

"This will involve us trying to look at a wide range of factors both inside and outside of the plant itself.

"Internal factors will include the detailed job histories of workers since they became employees at NSUK in Greenock.

"External factors will include their job histories before employment at the plant as well as lifestyle factors such, as smoking and diet."

Dr Osman confirmed that a nationwide study into cancer rates at all 25 semiconductor plants across England, Wales and Scotland was to be launched.

The health records of thousands of workers and former workers will be studied in a bid to obtain information about cancer rates across the industry as a whole.

Gerry Edwards said the firm would continue to cooperate

The next phase of the research at Greenock will involve finding details of job histories and lifestyles from workers who developed cancer, and from relatives of those who have died of the disease.

Gerry Edwards, vice president and managing director of the facility in Greenock, said the company was relieved at the findings.

He said the HSE would have ongoing support from the firm in the inquiry.

"We are relieved the HSE indicated there is no scientific evidence of increased cancer risk for employees working at our facility.

"Regardless, we pledge our support to cooperate fully in further investigation.

'Specific concerns'

"We have an excellent health and safety record and remain committed to maintaining a standard that ensure continual improvement in our performance."

Dr Mac Armstrong, Scotland's chief medical officer, said he welcomed "HSE and NSUK arrangements for providing information and counselling to workers past and present."

Some workers have launched legal action

Some workers at the plant have been involved in a damages action over claims that they have developed cancers and reproductive illnesses as a result of working there.

In 1999, they filed the action at a court in Santa Clare County in California - the headquarters of the firm, which opened the plant in the early 1970s.

Solicitor advocate Frank Maguire, of Glasgow firm Thompsons, has been heading the legal action in Scotland on behalf of support group Phase Two - People for Health and Safety in Electronics.

He said: "We note there are some indications in the study which warrant further investigation, as we have said before.

"Any study, in order to be credible, must cover a sufficient number of people in other facilities and in the general population.

"Meanwhile we are liaising with our American attorney colleagues with the situation regarding the legal action."