Anthrax may be the cause of death of three drug users, it has been revealed.
Health officials disclosed that a second person confirmed as having the disease has died.
And a third person who may have had the disease has also died.
But two other drug users with anthrax are alive and responding well to treatment.
The developments were disclosed by NHS Greater Glasgow and Clyde health board.
Officials said the board was working with police and colleagues at the neighbouring Lanarkshire health board to try to identify the source of the disease.
It is possible that contaminated heroin, or a contaminated cutting agent mixed with heroin, was responsible.
Dr Syed Ahmed, consultant in public health medicine, said: "There have been no new drug-injecting heroin users with infections admitted to hospitals in the west of Scotland since the weekend.
"I urge all drug-injecting heroin users to be extremely alert and to seek urgent medical advice if they experience an infection.
"Drug injecting is extremely risky and dangerous.
"The possible presence of a batch of heroin contaminated with anthrax makes drug injecting even riskier and even more dangerous."
But he said that, while drug users had to be on their guard, the risk of anthrax spreading to their families was negligible.
The two deaths from anthrax were in Victoria Infirmary and the Royal Infirmary, both in Glasgow.
The possible anthrax-linked death was also in the Royal Infirmary.
The two anthrax patients who survived are in Victoria Infirmary and Monklands District General Hospital in Lanarkshire.Reuse content