Live anthrax was sent by post to Belfast in a laboratory blunder.
A live sample of the deadly bacteria was accidentally sent by a Government laboratory in Surrey to one in Belfast in May 2012, official reports have revealed.
Scientists at the Animal Health and Veterinary Laboratories Agency (AHVLA) in Surrey meant to send harmless anthrax samples - which had been killed by heat - to a branch of the agency in Belfast.
Somehow, the tubes they were sending became mixed up. Instead of sending out dead material, the anthrax they sent to Northern Ireland was live and potentially deadly.
Luckily, the staff at the Belfast lab were not at risk due to the mistake, as the live anthrax was handled in a higher containment lab, according to documents from the Health and Safety Executive.
UK labs which study infectious organisms are rated by their containment level (CL): the higher the level of laboratory, the more barriers there are to prevent the escape of pathogens.
More dangerous pathogens, such as those that cause anthrax, the plague and rabies, can be handled in secure CL3 labs.
In a separate case, scientists at another AHVLA site opened live anthrax tubes in a less secure lab than the one in Belfast.
The anthrax was worked on in an open environment, where two unsuspecting staff were exposed to the bacteria - though both had been vaccinated and neither fell ill.
The Belfast incident prompted an immediate enforcement letter - a Crown Prohibition Notice - ordering the Surrey lab to shut down until improvements had been made.
The incident received little media coverage at the time.
Agri-food and Biosciences Institute Northern Ireland confirmed that it had received external quality assurance samples from the AHVLA in 2012 that were found to contain "some viable anthrax bacteria in very small numbers".
Professor James Dooley, Professor of Microbiology at the University of Ulster, said that the risk of anthrax was not as great as people feared.
"While the name anthrax may strike fear into everybody's hearts, that is not based on it killing loads of people around the world on a regular basis.
"Overall, the risks aren't that high. We have to keep on top of it, but it is not a big deal. There are very, very rigorous requirements for sending biological material through the post.
"If a protocol hasn't been followed correctly, it will be reported. It doesn't necessarily mean that anyone was at huge risk or anything like that."