A woman who injected heroin is being treated for the effects of anthrax following the death of another drug user.
Health officials in Glasgow believe the two hospital patients who tested positive for the deadly bacteria may have taken contaminated heroin.
A man died at the city's Victoria Infirmary on Wednesday, where the woman is now being treated.
Doctors are waiting for the results of tests carried out on a third drug user at Glasgow Royal Infirmary.
They are not yet linking the cases, all of whom had infections in areas of the body they injected with heroin.
Anthrax is a bacterial infection and occurs mostly in animals in Asia and Africa. Humans are rarely infected.
An outbreak control team set up by the Greater Glasgow and Clyde Health Board are meeting on Friday as they monitor the situation.
Public health consultant Dr Syed Ahmed said all health professionals and agencies working with people who inject themselves have been advised of the cases.
He said the risk to the general public was "negligible" but that all drug-injecting heroin users should seek urgent medical advice if they experience an infection.
"It is extremely rare for anthrax to be spread from person to person and there is no significant risk of airborne transmission from one person to another," he said.
