A Wednesday statement on the website of mobile operator O2 has revealed that a backup tape, which possibly contained the personal information of some customers, had been mislaid by the carrier's IT partner in Ireland, IBM.

Warning its customers about the loss of the `unencrypted' backup tape, O2 said that it was informed about the incident by IBM in summer this year, though the tape actually went missing in September 2011 and still remains unaccounted for. The O2 statement, however, stopped short of specifying the exact date on which IBM had told it about the mislaid backup tape.

While disclosing the data breach in its statement, O2 also said that it was asked to inform the customers about the mislaid tape by the Irish Data Protection Commissioner (DPC) who was apprised of the incident after the carrier got to know of it from IBM.

Although O2 said in its statement that there were approximately 1.3 million O2 customers in Ireland when the tape was lost in September last year, the company still did not make any disclosure about how many customer's details were on the tape.

Nonetheless, pointing out that some backup tapes hardly contain any customer data, O2 said that it believes "there is a low risk to customer data privacy;" and added: "The tape in question was one of a number produced on a daily basis containing a snapshot of certain data held on some of the company's systems at a particular moment in time."