Three women aged 23, 45 and 86 are recovering at home while a 71-year-old woman is also in hospital after contracting E.coli 0157, the National Health Service of Greater Glasgow and Clyde said.
A Scottish woman on holiday in Ireland had been taken to hospital with the bug but her condition showed 'no cause for concern', the head of the health provider's outbreak control team, Dr Sayed Ahmed, told a news conference.
An investigation is focusing on two Morrisons supermarkets in the town of Paisley, near Glasgow, and sliced cold meats bought from the delicatessen counters.
Samples and swabs taken from the stores concerned were being tested, with the results expected later in the week, Ahmed said, adding that it was too early to say whether the outbreak had been contained.
No other cases had come to light elsewhere in the country, he said.
In a statement, Morrisons, which is Britain's fourth-biggest supermarket chain, said it was 'deeply saddened' to hear that an elderly woman had died and others were ill.
'We are currently working closely with the authorities and although the full facts are not yet known, we have, as a precautionary measure, withdrawn sliced cold meat products from sale at the delicatessen counters of two stores in Paisley, Scotland,' it added.
'We advise anyone who has bought sliced cold meat products locally from the delicatessen counters in these two stores not to consume them.'
E.coli 0157 can cause serious illness, including stomach cramps, diarrhoea, nausea and fever. It is usually spread through contaminated food or drink.
The same strain of the bug killed 21 elderly people in Wishaw, also near Glasgow, in 1996.