Dozens of North Korean workers at the Gaeseong Industrial Complex have recently developed fevers and headaches due to possible exposure to toxic chemicals.

The Management Committee for the Gaeseong Industrial Complex said Wednesday that it suspended operations of production lines at the two car parts manufacturers as workers at the two factories had been showing symptoms of exposure to toxic chemicals since late last month.

South Korea’s Unification Ministry spokesman Lim Byeong-cheol said in a news briefing on Wednesday that North Korea has claimed its workers were poisoned by toxic chemicals, but a more professional epidemiological investigation is needed to confirm the claim.

The spokesman added that it is hard to determine whether an industrial accident occurred at the complex due to the North’s refusal to allow an inspection.