NHS Greater Glasgow and Clyde said the man died in Glasgow’s Victoria Infirmary on Wednesday. A woman being treated there has also tested positive.

A second man, who is being treated at treated at Glasgow Royal Infirmary, is being tested for the deadly anthrax bacterium. All three had infections in areas of the body they injected with heroin.

Doctors fear more people could die and have ordered tests on every drug user in Scotland who has been treated for infections over the past month.

Last night the health board said its public health protection team was working with the Procurator Fiscal and Strathclyde Police to identify the source of the anthrax.

One possibility being investigated is that contaminated heroin, or an agent used to cut the drug, may be to blame.

Dr Syed Ahmed, consultant in public health medicine, said: “I urge all drug-injecting heroin users to be alert and to seek urgent medical advice if they experience an infection. If you show any symptoms, please seek help immediately.”

However, as there is “no significant risk” of the spread of anthrax from person to person, neither the public nor relatives and friends of drugs users are thought to be at severe risk.

Although none of the victims has yet been identified, health officials revealed that the man who died had been battling the infection since December 9.

Anthrax was suspected of being responsible for a spate of deaths among Scottish heroin addicts in 2000.

New Scientist magazine reported that tests at the UK biological defence lab in Porton Down found signs of infection in dead addicts.

However, health officials in Glasgow, where several of the deaths occurred, insisted at the time that the drug users were not infected with anthrax.

The last two known anthrax-related deaths in Britain were both of men who made drums.

In 2006 Christopher Norris, 50, from Stobs, near Hawick, died after inhaling anthrax. Mr Norris made artworks and musical instruments, including drums.

Following the latest death, doctors fear cases may emerge beyond Glasgow. They will meet today to discuss the situation and are expected to release more details of the cases.

Explaining the theory about contaminated heroin, Dr Colin Ramsay, consultant epidemiologist with Health Protection Scotland, said: “It’s highly conceivable that it could have been contaminated either from the source in the origin country or it could have been contaminated as a consequence of subsequent cutting when it arrived in this country.”

He continued: “Heroin is not produced in a sterile environment. Most evidence suggest that heroin comes from countries where anthrax is present in the animal population. We’re not suggesting that someone deliberately added it.”

Dr Ahmed said: “One of the possibilities is that this bonemeal is used, bonemeal being produced from animals, that could be one of the sources, but this is speculation.

“We have no way of knowing how it might have got contaminated.”

An infection occurs in several stages. First, a small red pimple appears at the site where the infected ­heroin was injected. This pimple then grows into a blister, swells up and turns black. If treatment is not sought soon after this stage, the patient is likely to die of blood poisoning.

Symptoms can develop within a day or eight weeks, depending on the level of exposure.

A report from NHS Borders said Mr Norris is likely to have caught the disease after playing or handling anthrax-contaminated West African drums at a drumming workshop. Last November, drum-maker Fernando Gomez, who is thought to have inhaled anthrax spores while handling imported animal skins, died in hospital in London.

What is anthrax?

Anthrax is a bacterial infection, caused by the organism Bacillus Anthracis. It is quite rare in humans but occurs often in wild and domestic animals in Asia, Africa and some parts of Europe.

What does anthrax do to humans?

There are three forms of anthrax infection. In more than 95% of cases, the infection is cutaneous, which means it is contracted through direct physical contact with the skin or tissue of infected animals. Anthrax can also be contracted by inhaling spores or eating infected meat.

How common is anthrax in humans?

Extremely rare, although this has not always been the case. The disease was once known as “wool-sorters’ disease” and affected those who worked with animal

carcasses.

Can anthrax be treated?

Yes, in certain cases. If cutaneous anthrax is contracted, the disease can be treated and cured with antibiotics. However, inhalation or intestinal anthrax are much more difficult to treat adequately.

Am I at risk?

Probably not, although any drug users should be aware of the symptoms. While airborne transmission between people does occasionally occur, it is very rare for cutaneous anthrax to be spread.

Can I catch anthrax from animal hides?

Yes, but this is very rare. Anthrax is uncommon in UK livestock and no produce can be made from any animal that has died of the disease.