Ember Inns, which owns the Railway Hotel in Hornchurch in Essex, has said its food was prepared to the highest hygiene standards.
A spokesman told the London Evening Standard:
The local authority is investigating an alleged food poisoning outbreak at the Railway.
We are fully co-operating.
Until the investigation is complete we can’t speculate about a possible cause or source.
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Mladic, now 75, was the military commander of Bosnian Serb forces in the 1990s, who fought against the Bosnian Croat and Bosniak armies.
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His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."