Officials from the Department for Environment, Food, and Rural Affairs (Defra) have banned livestock movements within a five-mile radius around the farm at High Worsall near Yarm.
The investigations centred on a beef finishing unit, after vets began to suspect signs of the disease.
Final test results will not be known for several more days.
Chairman of the National Farmers Union (NFU) in North Yorkshire Derek Watson said "It looks as though it will not be positive but at least action has been taken instantly.
"This is what we need - if the worst came to the worst at least everything has been brought to standstill immediately and everybody is on top of the job and knows what to do."
The farm was an infected premises in May last year during the foot-and-mouth crisis.
A spokeswoman for the NFU said: "Such scares are not unusual in the aftermath of a major disease epidemic.
Previous scares
"The fact that this was picked up so quickly shows how vigilant the industry is being in checking stock.
"We are satisfied that Defra has taken all the action that should be taken to test for the disease."
None of the cattle on the farm have been slaughtered.
Since the last confirmed case of foot-and-mouth disease on 30 September 2001 there have been a number of investigations into suspected cases - none of which proved positive.