A "probable" new leak of the foot-and-mouth virus has been reported from an animal health facility in Surrey, the government has said.
The Pirbright site was the source of previous leaks
In a written statement, Environment Secretary Hilary Benn said the "internal" leak happened at the Merial laboratory at Pirbright.
Mr Benn added that an inspection team concluded that the virus was not released into the environment.
The virus is understood to have escaped through a leaking valve last week.
In his statement, Mr Benn said it was "possible that live FMD virus had entered the contained drainage system".
He added that from evidence gathered by inspectors, "they are assured that live virus has not been released to the environment."
The Department for Environment, Food and Rural Affairs (Defra) has confirmed that there will be no new livestock movement restrictions as a result of the latest suspected leak.
Merial shares the Pirbright site with the government's Institute for Animal Health.
Both facilities formed the focus for investigations into the previous foot-and-mouth outbreaks in Surrey in August.
Farming Minister Lord Rooker reiterated that there had been no escape of the disease from the Pirbright site and said there was no cause for panic.
"There's been no escape of foot and mouth. Something happened in the production process which was reported to us on Tuesday and full engineering work was done [on Wednesday]."
He added that the virus had only gone into the new drainage system and was picked up by checks on the first week of new production of the vaccine.
Defra has suspended Merial's licence and this will remain suspended while inspectors produce a full report.
Peter Ainsworth, shadow environment secretary, said: "News of another leak of foot-and-mouth virus at the government-licensed Pirbright site will shock the farming community, the British science community and the public.
"Hilary Benn now has some very urgent questions to answer."
Liberal Democrat environment spokesman Chris Huhne said: "It is a relief that the virus appears not to have leaked into the environment.
"However, we cannot have a situation where farmers in Surrey and across the country are in a constant state of fear that their livelihoods could be devastated by sloppy practice at a government-sponsored laboratory designed to protect them."
Investigations into the source of the virus in this summer's outbreak, carried out by the Health and Safety Executive and Imperial College, concluded leaking drains, heavy rain and building work at Pirbright were to blame.
However, the HSE was unable to say which of the two laboratories was at fault for releasing the virus.