Verizon Wireless said on Thursday that some employees had gained unauthorized access and viewed a personal cell phone account held by President-elect Barack Obama that is now inactive.
An Obama aide said his voice-mail messages and e-mails were not breached in the incident.
"We were notified yesterday that employees had accessed the records of an old cell phone no longer in use," the Obama aide said. "No voice or e-mails were listened to or read."
The company said the device in question was a simple voice phone, not a Blackberry or other device designed for e-mail or other data services.
In a statement, Verizon Wireless President and Chief Executive Lowell McAdam apologized to Obama and said all employees who had had access to Obama's account, whether authorized or not, were put on immediate leave with pay.
Telecom analyst Michael King of Gartner said that a telephone employee accessing billing information could likely see the numbers a customer had called, how long conversations with those people were and when he called them.
King said he could not recall a high-profile case where an employee had unauthorized access to records and that recent public cases involved company outsiders finding ways to check other people's records.
Verizon said it will soon impose disciplinary action against those who accessed Obama's account improperly.
Asked to disclose exactly what kind of information was viewed, the duration and frequency of the unauthorized access, Verizon Wireless spokesman Jeffrey Nelson declined comment beyond the company's statement.
Verizon Wireless is a venture of Verizon Communications and Vodafone Group.