Mike Stevens, from the Tywyn Chamber of Tourism and Commerce, says he is 'desperately concerned' for staff losing their jobs at the Halo Foods factory.
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There will be a fresher feel with temperatures falling lower than on recent nights.
The accident between junction 24, Coldra, and 23A, Magor, has closed the eastbound carriageway.
Eloise Parry, 21, died after taking diet pills containing the poisonous Dinitrophenol (DNP).