South Korea's Samsung Electronics has denied withholding crucial information from workers about which chemicals they have been exposed to at its factories.
The families of workers say there are about 200 cases of employees contracting serious diseases, including cancer, an investigation by the Associated Press news agency found.
Samsung withheld the information saying it came under trade secrets, said AP.
Samsung said the safety of its workers was its "number one priority".
Allegations 'not true'
A group of workers' families has said 76 people have died due to contact with the chemicals.
The victims need the information to qualify for compensation.
They allege Samsung withheld the information from South Korean authorities under the justification of trade secrets, an accusation the company firmly denied.
Analysis: Stephen Evan, South Korea correspondent
Proving causality with illness is notoriously difficult. Think of how long it took to get courts to recognise that smoking causes cancer or to accept the now undoubted fatal effects of asbestos.
Companies - and their highly skilled lawyers - can cast doubt on what exactly it was that a sick worker came into contact with which triggered the illness.
In the Samsung case, the Seoul Administrative Court ruled five years ago that though the precise cause of two Samsung workers' illness wasn't clear, "it can be construed that their exposures to dangerous chemicals and radiation were catalysts, at least."
Accordingly, it ordered that the Korean Workers' Compensation and Welfare agency should pay compensation. In the case of other workers, the court was not convinced of a direct link between the employer and employees' illnesses.
The issue now is whether Samsung is keeping back information which could help workers who fell ill making its products get compensation.
In South Korea, there is a frequent complaint that government and the conglomerates (with Samsung at the head) are too close for comfort - and for compensation to the families of those who died through work.
Under South Korean law, companies are not required to reveal information deemed a trade secret. Firms are, however, obliged to disclose whether their products contain toxic substances.
Samsung said in a statement that the allegation it had "intentionally blocked workers from accessing chemical information pertaining to workplace health and safety, or illegally prevented the disclosure of such information, is not true".
Compensation for industrial injury, including cancer, has been awarded in some cases, but the group of families say that other claims are being hampered because the South Korean authorities demand the details of which chemicals had caused the illnesses and deaths.
Without it, the authorities usually reject the demand for compensation.