The Oriental Star in Queensway, Bletchley, was closed by environmental health officers after a family of six became ill.
Milton Keynes Council said the owners had agreed to close the restaurant for cleaning on July 25 but when officers visited it again on July 30 they shut it down until further notice because of a risk to public health.
The results of tests conducted on the family are awaited as part of the environmental health and Health Protection Agency investigation.
The emergency prohibition notice will stay in place until inspectors are satisfied the owners have improved hygiene and food preparation standards.
Councillor Mike Galloway, cabinet member for the environment, said: "We are very pleased that prompt action was taken after the initial report, enabling us to make the necessary moves to ensure the health and safety of the public.
"I hope that the closure of Oriental Star sends out a clear message that dirty and unhygienic food premises will not be tolerated in Milton Keynes.
"The council will continue to clamp down on those proprietors who put at risk the health of those who work, live and visit the borough.
"It is essential that businesses take whatever steps are necessary to look after members of the public and also their own staff."
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