A laptop containing the personal information and bank account details of thousands of people and businesses has been stolen from Glasgow City Council.
The local authority is now contacting 37,835 affected customers, including suppliers and people receiving winter fuel payments and care grants.
Strathclyde Police and the Information Commissioner have been informed about the theft, which took place last month.
The laptop was password-protected but not encrypted.
It was one of two laptops stolen during a break-in at the council offices in Cochrane Street some time between Monday 28 and Tuesday 29 May.
The local authority said the full extent of the data loss did not become apparent until last Wednesday.
The information on the laptop relates to 17,692 companies and 20,143 individuals.
It includes names and addresses and, in the case of 16,451 customers, bank account details.
A full internal audit is being carried out.
A council spokesman said: “We are in the process of writing to the people affected by this theft to alert them to the data loss and offer them advice about what steps they might need to take.
“We’ve also provided them with a phone number they can use to contact us if they have any questions.
“We are sorry that this has happened and apologise for the inconvenience it has caused. Anyone with any information on the theft should contact Strathclyde Police.”
He added: “Customers should remember that no one from the council would ever call at their home or telephone them to ask for personal information, such as banking details.
“A bank will never ask for a customer’s PIN or for a whole security number or password.”
Affected customers can contact the council on 0141 287 0400.