Animals at a farm in Romney Marsh and at Chessington World of Adventures theme park were reported to show FMD symptoms and are being tested for the disease.
Defra chief veterinary officer Debby Reynolds said yesterday two suspected cases were being investigated.
Two new control zones have been set up around the Surrey theme park and the farm in Kent.
Chessington World of Adventures, which incorporates Chessington Zoo, is outside the restricted zone imposed in Surrey earlier this month after the foot-and-mouth outbreak was first detected.
In a statement, the park said it had called in vets and alerted Defra following concerns over one of its sheep.
A spokeswoman at the park said: "As a precautionary measure and because of the high state of alert currently in place due to the recent cases of foot-and-mouth disease, it was decided to immediately check all our cloven hoof stock for any signs of disease."