Staff at the National Semiconductors plant in Greenock are being urged to take part in a study into cancer levels at the factory.
There has been a previous study into cancer rates at the factory
Former staff say exposure to the chemicals used in the manufacture of silicon chips has left them more prone to serious illness.
A Health and Safety Executive (HSE) study proved inconclusive. A second investigation is now getting under way.
The HSE wants to speak to current and former workers at the plant.
It said initial research raised concerns about the level of lung, breast and stomach cancer in women and brain cancer in men.
The new study is being carried out by the HSE with the Institute of Occupational Medicine (IOM).
Researchers want to speak to workers or relatives who have suffered from such illnesses, as well as those who have not been affected.
Study leader Dr John Osman, from the HSE, said: "It is very important that we investigate our earlier findings as fully as possible.
"We want to understand if work at the factory may have affected cancer risks in the workforce.
"We need as many people as possible to respond positively to our request for help."