Farmers in Britain resumed sending animals to slaughter on Thursday after a ban on the movement of livestock to prevent an outbreak of foot and mouth disease from spreading was lifted in most of the country.

Cases of the disease have been found at two farms in Surrey, southern England. The government is set to confirm on Thursday whether animals culled overnight at a third farm on suspicion of having foot and mouth tested positive for the disease, said a spokeswoman for Britain's farm and environment ministry, Defra.

Test results are also expected on the drainage system of a research laboratory near the farms as investigators search for the source of the outbreak.

The results from both tests are expected to come through today, said the Defra spokeswoman.

The farm under suspicion is within a surveillance and protection zone set up on Friday after the first case was confirmed, and is close to the two affected farms.

Outside the outbreak area, relieved farmers transported their animals to abbatoirs after a movement ban was lifted at midnight, although they were subject to strict biosecurity measures to stop the spread of the disease.

NFU President Peter Kendall said the lifting of the movement ban was a first step on getting the industry back to normal but urged farmers to remain vigilant.

The return of the disease has raised fears of a repeat of a foot and mouth crisis in 2001 that devastated farming and cost Britain about 8.5 billion pounds ($17 billion).

Government inspectors have said there is a strong probability the disease originated in two research laboratories near the infected farms and are carrying out further tests.

Both laboratories, which develop vaccines against foot and mouth, handle the same rare strain of the virus that has struck the Surrey herds.

A preliminary report earlier this week said there was a possibility human movement had caused the release of the virus but investigators are also testing the drainage system at Merial Animal Health laboratory.

Merial -- owned by U.S. firm Merck and French firm Sanofi-Aventis SA -- shares a site in Pirbright, about 5 miles from the affected farms, with the government-run Institute for Animal Health.

Merial has said it has total confidence in its health and safety measures.

The European Union decided on Wednesday to maintain a ban on all British fresh meat, milk and live animal exports because of the outbreak. They will review the ban on August 23.

Britain's livestock industry has annual meat exports worth more than $1 billion and a long export ban would hit it hard.

The National Farmers' Union (NFU) estimates export curbs imposed this time cost farmers 1.8 million pounds a day.