Personal details of 37,000 Eir customers have been affected by a data breach, the telecommunications company has said.
In a statement, the company said that an unencrypted laptop was stolen on Sunday 12 August.
It contained personal details - including names, email addresses and Eir customer numbers, but no financial details - of 37,000 customers.
The theft happened "offsite", according to the company.
The firm has said that the breach was notified immediately to the Data Protection Commissioner and to gardaí.
They added that there is no evidence that the data at risk has been used by a third party.
A spokesperson said affected customers will be notified today.
Eir has said it is their policy that all company laptops should be encrypted and password protected.
They add that in this case, the laptop was decrypted by a faulty security update the previous working day.
This update affected a subset of company laptops and has been resolved, the company has said.