SEOUL, Aug. 27  -- Tens of workers from the Democratic People's Republic of Korea (DPRK), employed by South Korean companies running factories at the inter-Korean industrial zone, suffered fever and headaches due to possible benzene poisoning, local media reported Wednesday.

The DPRK employees, who work for two South Korean auto parts factories in the DPRK's border town of Kaesong, have sustained fever and headaches due to possible exposure to toxic chemicals since late last month, sources familiar with the matter were quoted by local media as saying.

The production lines, which make leather covers for a vehicle's steering wheel, have stopped operating since then, while other lines are operating normally.

South Korea's Unification Ministry spokesman Lim Byeong-cheol told a press briefing that no benzene and benzene mixture was used at the production lines according to the preliminary result of investigations conducted by the factory park's management committee.

To figure out whether toxic chemicals used at the lines led to sufferings of the DPRK workers, it needs to carry out an epidemiological investigation by experts, but the DPRK has opposed to the probe, the spokesman said.

Lim said South Korea has been conducting a precision probe into samples of chemicals used at the lines to find whether the chemicals caused the poisoning.

It would be the first time that DPRK workers suffer from toxic poisoning at the inter-Korean industrial zone if the poisoning proves true. Every year, 10-20 DPRK workers suffer from injuries at factories in Kaesong.

The spokesman said it will not be necessary for the South Korean government or companies to compensate for the injured DPRK workers as the firms there pay costs for social security along with wages.

But, he added that the auto parts makers should make efforts to improve the working environment if the poisoning proves true.